Inverting amplifier with signal feedback using NPN transistor

In this project about inverting amplifier, output voltage is fed back to input so as to cancel the effect of variation of temperature on voltage gain and improve stability of circuit with respect to temperature variations.

Inverting inputs are more preferred than the non-inverting ones due to the main benefit of stability. Inverting amplifiers, hence, even though provide less gain, are used for more applications. From various electronic circuits such as integrator or differentiator, inverting amplifiers are used in designing filters for communication circuits.

Without much change in the circuitry, inverting amplifiers can be made to work from AC to DC mode or vice versa. Hence, it becomes an easy task to design the circuits without giving much attention to the obvious power concerns.

Let's find out how to make an inverting circuit by using a transistor, a DC battery source and a few passive electronic components.

Lets understand the description of this project. When temperature changes for inverting amplifier, the output voltage changes. But such changes due to temperature can be minimised by use of signal feedback. In this circuit, a portion of output voltage is fed back to amplifiers input which has a negative effect on voltage gain but improves stability.

There are two ways to provide feedback. First way, as shown in figure 1 is to introduce a resistance

R3 between emitter and ground, by this input voltage gets divided between base–emitter P-N junction and voltage across new resistor, thereby increasing stability but decreasing voltage gain. The following table demonstrates the effect of feedback resistance.