Circuit Working Q1 is hooked up like a very traditional common emitter amplifier along with R2 supplying the base bias and R3 behaving like a collector load.

The input signal is transferred via the volume control RV1 and next through C1 to the Q1 base.

The collector load for Q1 consists of R1, R5 along with the loudspeaker.

The collector voltage of Q1 is around 50 of the supply voltage, i.e.

Within the intersection of the Q2, Q3 emitters the voltage may also be almost 4V5, R3 and R4 and extremely small value resistors to control the current passing across Q2 and Q3.

If the amplified input signal is no more than 4V5, Q2 is switched off (since the base will likely be at the reduced voltage compared to its emitter), nevertheless Q3 may continue to pass the signal.

As soon as Q1 amplifies the signal over 4V5 the situation gets reversed, Q2 switches ON and Q3 is switched off.

The signals are mixed at the the common emitter joint of Q2 and Q3, and transferred to the loudspeaker by means of the big electrolytic capacitor C2.

Smaller value for C2 capacitor can cause a weak reduced frequency response.

Negative feedback is supplied by R5 and R2, which guarantee stability by minimizing the gain marginally.

R1 is incorporated in order to get a tiny amount of base bias for Q2 and Q3; much more superior layouts make use of thermistors or diodes to protect against thermal runaway situations that could damage the pair of output transistor.

A negative aspect is the transistors DC coupling, where if one particular transistor shifts its characteristics the effect could be devastating Because of this, the output transistor pair must be a correctly matched pair.

Tiny Amplifier for Hearing Aid When a cheap and dirty audio mini amplifier circuit is what you are looking for, you can probably test out this little device.

Among various other factors, it could be accustomed to increase the output of a headphone for the people with hearing loss.

The circuit is a straightforward twin transistor, audio amplifier.

The 1st transistor, Q1, works like a basic medium gain preamp which obtains its signal coming from C1, acting like a DC blocker.

That transistor, next, feeds the signal to Q2, which is configured like the power amplifier stage.

This stage amplifies the signal even more, and C3 switches it towards the speaker.

You could possibly find a little bit of distortion, nevertheless this could be minimized through testing with different values of C5, maintaining it within the indicated range.

In case this does not work properly, consider some other values.

However thinking of how the gain of transistors can differ, it most likely will need quite a bit of experimenting to have all the things to function rightly.

Improved Miniature Hearing Aid Amplifier Circuit 4) Half Watt Amplifier Circuit The next miniature audio amplifier circuit presented here is quite easy.

This small amplifier is moderately sensitive and can provide 100 output having an input of approximately 50 mV.

Although this is not actually an active tone control, rather than a passive one, the effect is fairly adequate.

The volume control center arm is attached to the Q1 base through a DC blocking capacitor.

Audio Amp Schematic