Low distortion, low noise amplifier for high impedance circuits

Dual FETs are used in the input stage to reduce bias current and achieve high auxiliary
resistance to meet the requirements of the signal source. At the same time, in order to reduce high
distortion using the Miller effect, it is converted into current in the base ground circuits 5fTr2 and Tr8. control. Since
the current Miller circuit composed of 5fTr' and TrB becomes its load, the collector plate
output can obtain a large gain, and deep feedback can reduce nonlinear distortion. This
circuit is the most commonly used form of discrete component amplifier circuits.
    Tr. It is an ordinary constant current bias circuit, and the peripheral bias current resistor R can be said to set
the current exactly. The function of the zener diode Dl is to fix the drain voltage of Trt at
4~5vo.
    The OP amplifier is also an intermediate amplifier circuit. Part of it has always been composed of a
transistor differential circuit , but it has been simplified in the OP amplifier.