Simple Transistor Push Pull Speaker

Fig. 20- This complimentary amplifier provides up to 220 mW output with a frequency response from 90 Hz to 12.5 kHz. Although matched transistors are not required for Q2 and Q3t they are available as the 2N2707.

in the preamplifier. Resistive pads may be used to increase the input impedance, but they greatly reduce stage gain and increase problems with signal to noise ratios.

In the amplifier of Fig, 19 equalization is obtained by a frequency selective feedback path between the collector and base of QL Stabilization at dc is provided by the direct coupling between Q1 and Q2 and the current feedback path through the 10 ohm resistor in the base of Ql* In addition, more negative feedback is provided by the unbypassed emitter resistor in the second stage.

Complementary power amplifiers

The small transformerless complementary amplifier illustrated in Fig. 20 provides an output of 220 mW with an input of only 40 microamps. The transistors in the single ended class B out put stage are used in the common collector configuration and are biased by a resistive voltage divider and the driver transistor circuit. The emitter resistors in the output stage provide adequate temperature stability and are established by cut and try, but a value of 2.7 ohms seems to offer a good compromise, In adjusting this amplifier, the 100 ohm pot should be adjusted so that the idling current of the output transistor is on the order of 2.5 nA; this will insure a minimum of crossover distortion. When properly adjusted, this amplifier will exhibit a ±i

Amplifier Exhibits Two

16 OR ZZ ohms

50mw Audio Amplifier
Fig. 22, An audio power amplifier with push pull output using a single transistor in the final stage may be obtained with this simple circuit. Only about 50 mW is available from this amplifier, but the gain is flat up to 30 kHz. Both QI and Q2 should be germanium audio transistors such as

the 2N2I5, 2N404, 2N2953, SK3004 or HEP-253, clB frequency response from 90 Hz to 12.5 kHz and distortion of 4% at 120 mW input and 10% at 220 mW input.

Another complementary audio amplifier is shown in Fig, 21. This power stage provides 470 mW output and utilizes both ac and dc feed!jack to minimize distortion and extend frequency response. Although unmatched transistors are not required for the proper operation of this amplifier, a set of matched transistors is available as the 2N2707; the cost of the matched pair is onlv several cents more than the total separate costs of a 2N2706 and 2N2430. This very useful amplifier is flat ±3 dB from 15 Hz to 130 kHz, exhibits an input impedance of 750 ohms and produces less than 2% distortion at 470 mW output.

Single transistor push pull

The amplifiers illustrated in Figs, 22 and 23 illustrate how a quasi-push-pull output may be taken from a single transistor.

Quasi Complementary Circuit

Fig. 21, This 470 mW complementary audio amplifier exhibits less than 2% distortion and is flat within 3 dB from 15 Hz to 130 kHi.

Fig, 23, A target power version of the single transistor push pull circuit of Fig. 22 is shown here. The operating characteristics are similar to the 50mW circuit except that approximately I watt may be obtained. Transistors pi and Q 2 are 2N2I5, 2N404, 2N2953, SK3004 or HEP-253; Q3 is a 2N554, 2NI032, 2NI666, SK3009 or HEP-232, f


Circuit 500 Amplifier

Fig. 24. This line operated audio power amplifier provides about 500 mW output with an 80 millivolt input signal» Q I Is a

2N3565, 5E4002, SK3020 or HEP-54; Q2 is a 2N3916 or SE7005.


Fig. 24. This line operated audio power amplifier provides about 500 mW output with an 80 millivolt input signal» Q I Is a

2N3565, 5E4002, SK3020 or HEP-54; Q2 is a 2N3916 or SE7005.

These amplifiers are dc connected, thereby eliminating many components, while at the same time assuring excellent low frequency response.

In the circuit in Fig. 22, the first transittor serves as both an ac driver and part of the dc bias system. Although the values shown in the schematic were selected for optimum results, the 6800 ohm biasing resistor (Rl) should be adjusted experimentally to obtain equal voltages across the collector and emitter loads as illustrated in the schematic.

The frequency response of this amplifier may be adjusted by changing the value of the 0,05 ¿iF capacitor (CI), When this capacitor is left completely out of the circuit, the heavy negative feedback around the circuit provides a frequency response that is flat from dc (with the input capacitor shorted) to 30 kHz, However, under these conditions, the gain is only about 35 dB, The maximum power output available from tins circuit is on the order of 50 m\V; above ar this level severe clipping occurs with noticeable audible distortion.

A higher power circuit that exhibits essentially the same characteristics is illustrated in Fig. 23, With properly heat sinked transistors, this unit provides usable outputs up to one watt. As with the lower power circuit, the bias resistor (Rl) should be adjusted to provide equal voltages across the emitter and collector loads shown in the schematic.

The input impedance of both these circuits is on the order of several thousand ohms, so they may be easily driven by other transistor circuits. Although two separate speakers are shown as the output load, the load could just as easily be two separate transformer windings.

Line operated amplifiers

The line operated one watt amplifier in Fig. 24 provides about 500 mW output with an 80 mV input signal. The use of transistors with high collector to emitter voltage ratings permits the use of a transformerless power supply operating directly from the 115 volt ac line. To prevent damage to Q2 in the event ot transient voltage spikes on (lie line, a voltage dependent resistor (VDR) such as a Genera Electric 1 hyrector or Motorola Thyristor should be connected across the primary of the output transformer.

Another line operated power amplifier is illustrated in Fig, 25- This amplifier is t IOO v

Amplificatore Push Pull Transistor

ot 2NE92S, ENSiSt, QZ-2HZ9Z*, ZHZ?tZ, 2NJ393 03-2N232}, q4-zn4054

Fig. 25, High performance with low cost is obtained with this line operated audio power amplifier because expensive electrolytic capacitors are eliminated by direct coupling between stages. This circuit delivers I watt to the speaker with 3 mW input.

Direct Coupling AmpAmplificatore Push Pull Transistor

g2 2nm04. 5e60gi

ZS2Q&&, 2N3HQ, ZN3923

Fig, 27. 5 watt modulator for transmitters up to 10 watts input. High gain silicon transistors and transformer coupling increase performance at decreased circuit complexity.

ters, The circuit is relatively straight forward, wit ^ i a single audio amplifier driving the class li push pull power stage through a small transformer. To modulate the collector ol a small transmitter, simply run the collector voltage supply through the secondary of the mo( luation transformer, in this case a )o\v cost 5k:200 ohm audio transformer-

The 5 watt modulator shown in Fig. 27 may he used to modulate transmitters with lij) to 10 watts input. The use of low cost, high gain silicon transistors and efficient transformer coupling significantly decreases the complexity of the circuit. Usually many more transistors are required to obtain five watts of audio with a microphone input. Although this modulator was designed for a ceramic or crystal microphone, it may be used with dynamic types with slightly less gain. This circuit exhibits extremely low distortion characteristics, and when used to collector modulate a ten watt transistor transmitter, produces extremely clear and crisp audio.

The transistorized 25 watt modulator shown in Fig* 28 is not much different from other types which have been described, but with three transformers it is somewhat more efficient than most The transformers are readily available commercial models which may be obtained from most suppliers. However, transformer 12 must have a center tap on the secondary; this is easi y accomplished by unwinding 46 turns from (lie outside winding, bringing out a center tap at this point and rewinding. Impedance matching to the rf amplifier is accomplished by adjusting the rf output loading network.

tl 25k 1200 ohms t2 20 k 2k ohms ct

Fig. 26. This 100 mW modulator may be used to collector modulate transmitters up to about 200 mW or to base modulate somewhat larger power amplifiers. Good performance w i+h a minimum of components is obtained by transformer coupling between stages.

based on the use of a high voltage plastic transistor, the 2N4054* ¡"he circuit delivers one watt of audio power to a speaker with about 3 millivolts input signal; at this power level the total harmonic distortion at kHz is less than 10%, The key to its low cost performance is the fact that direct coupling is used, thereby eliminating the need for expensive electrolytic capacitors.


The 100 milliwatt modulator illustrated in Fig. 26 is suitable for collector modulating small transistor transmitters up to about 200 milliwatts, It mav also be used for base modulating somewhat larger transmit

Patent Number For Reverso Watch

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  • Daria
    How to design transistor amplifier push and pull?
    3 years ago
  • cupido
    How to lower harmonics and crossover in audio using only transistors?
    2 years ago
  • Norman
    How transistor push large speakers circuit diagrams?
    1 year ago
    How to speaker amplifier circuit using tramsitor?
    1 year ago
  • Gregory
    How three transistor amp damage large speakers circuit diagrams?
    1 year ago

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