Amplifier stage with switchable gain and reduced distortion

摘要

An amplifier stage comprising differential pairs T1 and T2 is provided with resistive ladders R1... R2n connected between the second control electrodes of the differential pair. The taps on the mirror locations along the resistive ladder R1... R2n are switchable connected to the first and second current source transistors T3, T4, the current source transistors being the first of the transistors forming a differential pair. With their control electrodes connected to the main electrodes. By placing the switches in series with the current source transistors T3 and T4, the effects of the nonlinear impedance of the switches are reduced to a negligibly small rate since the output impedance of the current source transistors T3 and T4 is significantly higher than the impedance of the switches. do. Thus a linear conversion impedance is obtained and the amplifier stage is switchable in gain and distortion is reduced.