Radio amateurs need to receive various radio signals. This requires the presence of an LF and HF generator. Often, this type of device is called a transistor generator for its design feature.
Additional Information. A current generator is a self-oscillating device created and used to generate electrical energy in the network or convert one type of energy into another with a given efficiency.
Self-oscillating transistor devices
The transistor generator is divided into several types:
- by the frequency range of the output signal;
- by the type of signal issued;
- according to the algorithm of action.
The frequency range is usually subdivided into the following groups:
- 30 Hz-300 kHz - low range, indicated by low frequencies;
- 300 kHz-3 MHz - middle range, indicated by midrange;
- 3-300 MHz - high range, indicated by HF;
- more than 300 MHz - ultra-high range, indicated by microwave.
This is how radio amateurs divide the ranges. For audio frequencies, a gap of 16 Hz-22 kHz is used and it is also divided into low, medium and high groups. These frequencies are found in any household sound receiver.
The following division is based on the type of signal output:
- sinusoidal - a sinusoidal signal is output;
- functional - at the output the signals have a specially specified shape, for example, rectangular or triangular;
- noise generator - a uniform frequency range is observed at the output; ranges can be different, depending on the needs of the consumer.
Transistor amplifiers differ in their algorithm of action:
- RC - main area of \u200b\u200bapplication - low range and audio frequencies;
- LC - main area of \u200b\u200bapplication - high frequencies;
- Blocking Generator - Used to produce high duty cycle pulse signals.
Image on electrical diagrams
First, let's look at getting a sinusoidal type of signal. The most famous transistor generator of this type is the Colpitz oscillator. This is a master oscillator with one inductance and two capacitors connected in series. With the help of it, the required frequencies are generated. The remaining elements provide the required mode of operation of the transistor at constant current.
Additional Information. Edwin Henry Kolpitz was the head of innovation at Western Electric at the beginning of the last century. Was a pioneer in the development of signal amplifiers. For the first time produced a radiotelephone, which allows to talk across the Atlantic.
The Hartley master oscillator is also widely known. It, like the Kolpitz circuit, is quite simple to assemble, however, an inductance with a tap is required. In the Hartley circuit, one capacitor and two inductors connected in series produce oscillation. Also in the circuit there is an additional capacity for receiving positive feedback.
The main field of application of the above devices is medium and high frequencies. They are used to obtain carrier frequencies, as well as to generate electrical oscillations of low power. Home radio receivers also use oscillators.
All of these areas of application do not tolerate unstable reception. For this, another element is introduced into the circuit - a self-oscillating quartz resonator. In this case, the accuracy of the high-frequency generator becomes practically reference. It reaches millionths of a percent. In the receiving devices of radio receivers, exclusively quartz is used to stabilize the reception.
When it comes to low-frequency and sound generators, there is a very serious problem. An increase in inductance is required to increase tuning accuracy. But an increase in inductance leads to an increase in the size of the coil, which greatly affects the size of the receiver. Therefore, an alternative scheme of the Colpitz generator was developed - the Pierce low-frequency generator. There is no inductance in it, and a self-oscillating quartz resonator is used in its place. In addition, the quartz resonator allows the upper vibration limit to be cut off.
In such a circuit, the capacitance prevents the constant component of the base bias of the transistor from reaching the resonator. Signals up to 20-25 MHz, including sound signals, can be generated here.
The performance of all considered devices depends on the resonant properties of the system, consisting of capacitors and inductors. It follows that the frequency will be determined by the factory characteristics of the capacitors and coils.
Important! A transistor is an element made from a semiconductor. It has three outputs and is capable of controlling a large output current from a small input signal supplied. The power of the elements is different. Used to amplify and switch electrical signals.
Additional Information. The presentation of the first transistor was carried out in 1947. Its derivative, the field-effect transistor, appeared in 1953. In 1956. for the invention of the bipolar transistor was awarded the Nobel Prize in Physics. By the 80s of the last century, vacuum tubes were completely replaced from radio electronics.
Functional transistor generator
Functional oscillators based on self-oscillating transistors are invented for the production of methodically repeating signal-pulses of a given shape. Their shape is set by a function (the name of the entire group of such generators appeared as a result of this).
There are three main types of impulses:
- rectangular;
- triangular;
- sawtooth.
A multivibrator is often cited as an example of the simplest low-frequency manufacturer of square-wave signals. He has the simplest diagram for DIY assembly. Radio electronics engineers often start with its implementation. The main feature is the absence of strict requirements for the ratings and shape of transistors. This is due to the fact that the duty cycle in the multivibrator is determined by the capacitances and resistances in the electrical circuit of the transistors. The frequency on the multivibrator is in the range from 1 Hz to several tens of kHz. It is impossible to organize high-frequency vibrations here.
Obtaining sawtooth and triangular signals occurs by adding an additional chain to a typical circuit with rectangular pulses at the output. Depending on the characteristics of this additional chain, rectangular pulses are converted into triangular or sawtooth pulses.
Blocking generator
At its core, it is an amplifier assembled on the basis of transistors located in one stage. The area of \u200b\u200bapplication is narrow - a source of impressive, but transient in time (duration from thousandths to several tens of microseconds) pulse signals with a large inductive positive feedback. The duty cycle is more than 10 and can reach several tens of thousands in relative terms. There is a serious sharpness of the fronts, which practically do not differ in shape from geometrically regular rectangles. They are used in screens of electron-beam devices (kinescope, oscilloscope).
Field effect transistor pulse generators
The main difference between field-effect transistors is that the input resistance is commensurate with the resistance of electronic tubes. The Kolpitz and Hartley circuits can also be assembled on field-effect transistors, only coils and capacitors must be selected with the appropriate technical characteristics. Otherwise generators on field effect transistors will not work.
The frequency chains follow the same laws. For the production of high-frequency pulses, a conventional device assembled using field-effect transistors is better suited. The field-effect transistor does not shunt inductance in circuits, so RF signal generators work more stably.
Regenerators
The LC circuit at the generator can be replaced by adding an active and negative resistor. This is a regenerative way to get an amplifier. This circuit has positive feedback. Due to this, losses in the oscillatory circuit are compensated. The described circuit is called regenerated.
Noise generator
The main difference is the uniform response of the LF and HF frequencies in the required range. This means that the amplitude characteristics of all frequencies in this range will not differ. They are mainly used in measuring equipment and in the military industry (especially aircraft - and rocketry). In addition, it is used to perceive sound by the human ear - the so-called "gray" noise.
A simple do-it-yourself sound generator
Let's consider the simplest example - a howler. Only four elements are needed: a film capacitor, 2 bipolar transistors and a tuning resistor. The load will be an electromagnetic emitter. A simple 9V battery is enough to power the device. The operation of the circuit is simple: a resistor sets the offset to the base of the transistor. Feedback occurs through the capacitor. The tuning resistor changes the frequency. The load must be of high resistance.
With all the variety of types, sizes and forms of execution of the considered elements, powerful transistors for ultrahigh frequencies have not yet been invented. Therefore, oscillators on transistors of self-oscillation are used mainly for the low and high frequency ranges.
Video
Sound generator type "ZG-10"
Purpose and scope
The sound generator of the "ZG-10" type is a portable laboratory device designed to produce sinusoidal AC voltages of low frequency.
It was manufactured according to the technical specifications TU No 0.506.020-54 and is designed for operation at an ambient temperature of +10 to +30 degrees. C and relative humidity up to 80%.
The device of the "ZG-10" type is used for adjusting and testing low-frequency stages of radio equipment in laboratory and workshop practice.
Main technical characteristics
- The range of generated frequencies from 20 to 20,000 Hz is divided into three sub-bands:
a) 20 - 200 Hz with a multiplier x1;
b) 200 - 2000 Hz with a multiplier of x10;
c) 2000 - 20,000 Hz with a multiplier of x100. - Frequency calibration error does not exceed + -2% + - 1 Hz.
- Frequency instability when the supply voltage changes by + -10% of the nominal does not exceed + -0.2%.
- The frequency change after 30 minutes of preheating does not exceed 3 Hz at a frequency of 1000 Hz for the first hour of operation and 4 Hz for the next seven hours of operation.
- The maximum output voltage is 150 V at a maximum power of 5 W.
- The device output is designed for balanced and unbalanced loads with impedance of 50, 200, 600 or 5000 ohms.
- The unevenness of the frequency response relative to the normal level at a frequency of 400 Hz does not exceed + -1.5 dB.
- When the supply voltage changes by + 10%, the output power changes by no more than + 5%.
- The nonlinear distortion factor does not exceed 0.7%.
- Output voltage indicator with a measurement limit of 60 V. The indicator scale calibration error at a frequency of 1000 Hz and with a load of 600 Ohm does not exceed + -5%.
- The output voltage is adjustable:
a) smoothly - within the range from zero to the maximum value;
b) in steps - every 1 dB to 110 dB using two dividers - the first one, in steps every 10 to 100 dB and the second, every 1 dB to 10 dB.- The following lamps are used in the device: 6Ж8 - 1 pc .; 6P9 - 1 pc.; 6Н8С - 1 pc .; 6S4S - 2 pcs.; 5TS3S - 1 pc .; 6Х6С - 1 pc. and TP-6/2 1 pc.
- The device is powered from an alternating current with a frequency of 50 Hz and a voltage of 110, 127 or 220 V + -10%.
- Power consumption 150 watts.
- The overall dimensions of the device are 598 x 357 x 293 mm.
- The weight of the device is about 35 kg.
The scheme of the sound generator of the "ZG-10" type consists of the following main elements: a generator, an amplifier, an output voltage indicator, an output device and a rectifier.
The generator is a two-stage amplifier, assembled on 6Zh8 and 6P9 tubes and excited with the help of positive feedback, which is carried out by a phasing chain consisting of resistances and capacitors and providing excitation of the generator at a frequency set by the parameters of this chain. Changing the generator frequency is carried out by changing the parameters of the phasing chain.
The oscillator circuit is covered with negative feedback, ensuring frequency stability and minimum harmonic distortion.
The negative feedback circuit uses a thermistor, which, as a nonlinear resistance, ensures that the amplitude of the generated signal remains constant.
The amplifier is assembled according to a two-stage scheme on 6H8C, 6C4C and 6C4C tubes. The first stage, assembled on a 6Н8С lamp, is a phase inverter. The second stage, assembled on two 6C4C tubes, is a push-pull power amplifier.
The output voltage indicator is a lamp voltmeter, arranged according to a full-wave rectifier circuit, assembled on a 6X6C lamp. A magnetoelectric device of the M5 type of class 2.5 is used as an indicator.
The output device consists of two dividers, assembled according to the bridge and matching transformer scheme. The first divider gives attenuation up to 100 dB in steps of 10 dB and the second up to 10 dB in steps of 1 dB.
The matching transformer is used to match the generator output with a load of both balanced and unbalanced resistance of 50, 200, 600 or 5000 Ohm.
The rectifier is assembled according to a full-wave circuit on a 5Ts3S lamp with a two-link L-shaped filter. The rectifier is powered from an alternating current with a frequency of 50 Hz and a voltage of 110, 127 or 220 V.
Design
The device is assembled and mounted on a metal vertical panel and a horizontal chassis, placed in a metal casing equipped with carrying handles. The front panel of the device contains:
- frequency setting knob with dial;
- output voltage indicator;
- indicator light;
- power switch;
- multiplier switch;
- knob for setting the output voltage;
- load switch;
- output terminals;
- switch for "high-resistance load";
- two switches for attenuators of the output device.
http://flowmetrika.narod.ru/_pribori_docs/
SOUND FREQUENCY GENERATOR GZ-2 (ZG-10)
Figure: 1. Generator GZ-2.
The sound frequency generator GZ-2 (Fig. 1) is intended for use as a source of sinusoidal electrical oscillations of sound (low) frequency.
The device is designed for use in laboratory conditions and repair shops.
MAIN TECHNICAL CHARACTERISTICS
Generated frequency range from 20 to 20,000 hzdivided into three sub-ranges: 20-200; 200-2000 and 2000-20,000 hz.
Frequency setting error ± 2% ± 1 hz.
Frequency drift after 30 minpreheating for the first hour of operation no more than ± 0.4%; for the next seven hours of operation, additional frequency drift is not more than ± 0.4%.
Normal output power 0.5 tue.
Maximum output power 5 tue
Maximum output voltage at matched load 150 at.
The change in the output voltage is carried out smoothly, as well as in steps through 1 dbfrom 0 to 110 dbusing two dividers: the first - after 10 dbfrom 0 to 100 db,the second - after 1 dbfrom 0 to 10 db.
The generator output impedance is rated for 50 matched loads; 200; 600 and 5000 ohm.
Harmonic distortion factor:
10. Frequency response unevenness relative to readings at a frequency of 400 hz:
at maximum output power and at all loads at frequencies from 50 to 10,000 hzno more than ± 1 db,at frequencies from 20 to 20,000 hzno more than ± 3.5 db;
at normal output power at matched load 600 ohmat frequencies from 50 to 10,000 hzno more than ± 0.5 db,at frequencies from 20 to 20,000 hzno more than ± 1.5 db.
The indicator scale calibration error at a frequency of 1000 hzat voltage up to 60 atdoes not exceed ± 5%.
Power supply of the device from an alternating current with a frequency of 50 hz,software voltage; 127 or 220s ± 10%.
Power consumption from the network no more than 150 wah.
Dimensions: 598x357x293 mm.
Device weight no more than 35 kg.
DESCRIPTION OF THE PRINCIPAL DIAGRAM
Generator ГЗ-2 (Fig. 2) consists of the following main elements: master oscillator, amplifier, output voltage indicator, output device and power supply.
The master oscillator is assembled according to a rheostat-capacitive circuit on lamps L 1 (6Ж8) and L 2 (6P9). An abrupt change in the generator frequency is carried out by switching resistances R 1 -R 11 , and smooth - by changing the capacity FROM 1 . To increase the stability of the generator, a negative feedback is introduced into its circuit, in the circuit of which a thermistor TP6 / 2 is connected.
The phase inverter stage of the audio frequency amplifier is made according to the autobalanced symmetrical circuit on the lamp L 3 (6H8C). Dual tube power amplifier L 4 and L 5 (6S4C) operates on a push-pull circuit. The gain of the audio amplifier is about 4.
The output indicator is a diode voltmeter assembled in a full-wave circuit on a lamp L 8 (6X6C). A magnetoelectric device M5 of class 2.5 IP 1 with a scale of 60 was used as an indicator at,calibrated in effective voltage values \u200b\u200bat a load of 600 ohm.The output device consists of two attenuators - bridge-type voltage dividers U 1 per 100 dbwith steps of 10 dband Have 2 on 10 dbwith steps of 1 dband transformer Tr 3 , serving to match the generator output with loads of 50; 200; 600 and 5000 ohm.A full-wave rectifier on a lamp is used as a power source L 7 (5CZS) with a two-link L-shaped filter.
All oscillator lamps (with the exception of the amplifier output stage lamps) can be replaced with the same type without tuning the generator. When changing lamps L 4 and L 5 (6C4C) it is necessary to select them so that the background level at the generator output does not exceed 15 mv.When measuring the background at frequencies from 4000 to 10000 hzhandle Reg. out. ex.R 22 should be set to the extreme left, the handle Out. resistance B 2 - in position 600, switch Internal load B 4 - in position Incl.
WORKING WITH THE DEVICE
Set the fuse to the position corresponding to the mains voltage.
Connect the power cord plug to a 50 hz,turn on the mains toggle switch, after which the signal light should come on.
The exact frequency setting is made after a 30-minute warm-up.
Frequency setting
Frequencies of the first sub-band 20-200 hz Factoris in position × 1. The frequency in hertz corresponds to the scale reading.
Frequencies of the second sub-band 200-2000 hzset by turning the scale, while the switch Factoris at the × 10 position, the scale reading is multiplied by 10.
Frequencies of the third sub-band 2000-20 000 hzset by turning the scale, while the switch Factoris at x100, the scale reading is multiplied by 100.
Setting the amplitude, output voltage
1. The amplitude of the output voltage is smoothly adjusted by the knob Reg. out. egand in steps through 1 dbfrom 0 to 110 db- handles Attenuation dB.
The dial gauge directly measures the output voltage at a load of 600 ohmand output attenuators (switch Out. resistancein position 600 ohm).
When the generator is operating at loads of 50; 200 and 5000 ohmswitch Out. resistanceit is necessary to put in the position corresponding to the load value, the readings of the dial gauge are multiplied by 0.289; 0.576 and 2.89, respectively. In this case, the toggle switch is in the position OffIf the load differs from the above, then it is impossible to read on the scale of the device.
When the generator is operating on a device with a large input resistance, it is necessary to turn on the toggle switch and the switch Out. resistanceput in any of four positions, depending on the value of the required voltage. In this case, the readings of the indicator scale are multiplied by the corresponding coefficients.
Low frequency generators (LFOs) are used to obtain continuous periodic oscillations of electric current in the frequency range from fractions of a Hz to tens of kHz. Such generators, as a rule, are amplifiers covered by positive feedback (Fig. 11.7, 11.8) through phase-shifting chains. To implement this connection and to excite the generator, the following conditions are necessary: \u200b\u200bthe signal from the amplifier output must enter the input with a phase shift of 360 degrees (or a multiple of it, i.e. O, 720, 1080, etc. degrees), and itself the amplifier should have some gain margin, KycMIN. Since the condition of the optimal phase shift for the occurrence of lasing can be fulfilled only at one frequency, it is at this frequency that the amplifier with positive feedback is excited.
To shift the signal in phase, RC and LC circuits are used, in addition, the amplifier itself introduces a phase shift into the signal. To obtain positive feedback in the generators (Fig. 11.1, 11.7, 11.9), a double T-shaped RC-bridge is used; in generators (Fig. 11.2, 11.8, 11.10) - Wine bridge; in generators (Fig. 11.3 - 11.6, 11.11 - 11.15) - phase-shifting RC-chains. In generators with RC chains, the number of links can be quite large. In practice, to simplify the scheme, the number does not exceed two or three.
Calculation formulas and ratios for determining the main characteristics of RC generators of sinusoidal signals are given in Table 11.1. For simplicity of calculation and simplification of the selection of parts, elements with the same denominations were used. To calculate the generation frequency (in Hz), the values \u200b\u200bof the resistances, expressed in Ohms, are substituted into the formulas, and the values \u200b\u200bof capacities - in Farads. For example, let's determine the frequency of generation of an RC-generator using a three-link RC-chain-pi positive feedback (Fig. 11.5). At R \u003d 8.2 kΩ; C \u003d 5100 pF (5.1x1SG9 F) the operating frequency of the generator will be 9326 Hz.
Table 11.1
In order for the ratio of the resistive-capacitive elements of the generators to correspond to the calculated values, it is highly desirable that the input and output circuits of the amplifier, covered by a positive feedback loop, do not shunt these elements, do not affect their value. In this regard, for constructing generator circuits, it is advisable to use amplification stages with high input and low output impedances.
In fig. 11.7, 11.9 show "theoretical" and simple practical generator circuits using a double T-bridge in the positive feedback circuit.
Wien bridge generators are shown in Fig. 11.8, 11.10 [P 1 / 88-34]. A two-stage amplifier is used as the ULF. The amplitude of the output signal can be adjusted with potentiometer R6. If you want to create a generator with a Wien bridge, tunable in frequency, in series with the resistors R1, R2 (Fig. 11.2, 11.8) include a double potentiometer. The frequency of such a generator can also be controlled by replacing the capacitors C1 and C2 (Fig. 11.2, 11.8) with a double variable capacitor. Since the maximum capacitance of such a capacitor rarely exceeds 500 pF, it is possible to tune the oscillation frequency only in the region of sufficiently high frequencies (tens, hundreds of kHz). The stability of the generation frequency in this range is low.
In practice, switched sets of capacitors or resistors are often used to change the generation frequency of such devices, and field effect transistors are used in the input circuits. In all the schemes given there are no elements for stabilizing the output voltage (for simplicity), although for generators operating at the same frequency or in a narrow range of its tuning, their use is not necessary.
Circuits of generators of sinusoidal signals using three-link phase-shifting RC-chains (Fig.11.3)
are shown in Fig. 11.11, 11.12. The generator (Fig. 11.11) operates at a frequency of 400 Hz [P 4 / 80-43]. Each of the elements of the three-link phase-shifting RC-chain introduces a phase shift of 60 degrees, with a four-link one - 45 degrees. A single-stage amplifier (Fig. 11.12), made according to the scheme with a common emitter, introduces a 180-degree phase shift necessary for generation to occur. Note that the generator according to the diagram in Fig. 11.12 is efficient when using a transistor with a high current transfer ratio (usually over 45 ... 60). With a significant decrease in the supply voltage and a non-optimal choice of elements for setting the DC mode of the transistor, the generation will fail.
Sound generators (Fig. 11.13 - 11.15) are similar in construction to generators with phase-shifting RC-chains [Rl 10 / 96-27]. However, due to the use of inductance (telephone capsule TK-67 or TM-2V) instead of one of the resistive elements of the phase-shifting chain, they work with a smaller number of elements and in a larger range of supply voltage variation.
So, the sound generator (Fig. 11.13) is operational when the supply voltage changes within 1 ... 15 V (current consumption is 2 ... 60 mA). In this case, the generation frequency changes from 1 kHz (ipit \u003d 1.5 V) to 1.3 kHz at 15 V.
The sound indicator with external control (Fig. 11.14) also works at 1) power \u003d 1 ... 15 V; the generator is turned on / off by applying logic levels of one / zero to its input, which should also be within 1 ... 15 V.
The sound generator can be made according to another scheme (Fig. 11.15). Its generation frequency varies from 740 Hz (current consumption 1.2 mA, supply voltage 1.5 V) to 3.3 kHz (6.2 mA and 15 V). The generation frequency is more stable when the supply voltage changes within 3 ... 11 V - it is 1.7 kHz ± 1%. In fact, this generator is no longer made on RC, but on LC-elements, moreover, the winding of the telephone capsule is used as the inductance.
The low-frequency generator of sinusoidal oscillations (Fig. 11.16) is assembled according to the "capacitive three-point" circuit characteristic of LC generators. The difference lies in the fact that a telephone capsule coil is used as the inductance, and the resonant frequency is in the range of sound vibrations due to the selection of capacitive circuit elements.
Another low-frequency LC-oscillator, made according to the cascode scheme, is shown in Fig. 11.17 [P 1 / 88-51]. As an inductance, you can use a universal or erasing heads from tape recorders, windings of chokes or transformers.
RC-generator (Fig. 11.18) is implemented on field-effect transistors [Rl 10 / 96-27]. A similar scheme is usually used when building highly stable LC generators. Generation occurs already at a supply voltage exceeding 1 V. When the voltage changes from 2 to 10 6, the generation frequency decreases from 1.1 kHz to 660 Hz, and the current consumption increases, respectively, from 4 to 11 mA. Pulses with a frequency from units of Hz to 70 kHz and above can be obtained by changing the capacitance of the capacitor C1 (from 150 pF to 10 μF) and the resistance of the resistor R2.
The above sound generators can be used as economical indicators of the state (on / off) of nodes and blocks of electronic equipment, in particular, light-emitting diodes, for replacing or duplicating light indication, for emergency and alarm indication, etc.
Literature: Shustov M.A. Practical Circuitry (Book 1), 2003
This article describes a simple audio frequency generator, in other words, a buzzer. The circuit is simple and consists of only 5 elements, excluding the battery and the button.
Description of the scheme:
R1 sets the offset to VT1 base. And with the help of C1, feedback is carried out. The speaker is a VT2 load.
Assembly:
So, we need:
1) A complementary pair of 2 transistors, that is, one NPN and one PNP. Almost any low-power will do, for example KT315 and KT361. I used what was at hand - BC33740 and BC32740.
2) Capacitor 10-100nF, I used 47nF (marking 473).
3) Trimmer resistor about 100-200 kOhm
4) Any low-power speaker. Headphones can be used.
5) Battery. Almost anything is possible. Finger, or crown, the difference will be only in the frequency of generation and power.
6) A small piece of foil-clad fiberglass, if you plan to do everything on the board.
7) Button or toggle switch. I used a button from a Chinese laser pointer.
So. All details are collected. Let's start making the board. I made a simple surface mount board mechanically (i.e. with a cutter).
So, everything is ready for assembly.
First, we mount the main components.
Then we solder the power wires, a battery with a button and a speaker.
The video shows the operation of the circuit from a 1.5V battery. A trimmer resistor changes the oscillation frequency
List of radioelements
| Designation | A type | Denomination | number | Note | Score | My notebook |
|---|---|---|---|---|---|---|
| VT1 | Bipolar transistor | KT315B | 1 | Into notepad | ||
| VT2 | Bipolar transistor | KT361B | 1 | Into notepad | ||
| C1 | Capacitor | 10-100nF | 1 | Into notepad | ||
| R1 | Resistor | 1-200 kΩ | 1 |