Closed loop amplification circuit and by RL and. Decided, when magnification is 100 times (40dB), the input signal is high, in order to ensure a stable circuit work for, people
in the secondary circuit plus the variable resistor VRi attenuation. Because shoot summarized Jiangxi people circuit, the feedback resistor is not too large, so take a small lead 2 resistance. Close to the maximum output, it is easy to cause oscillation, so the addition of the capacitor Cl. Cl.