Circuit connecting the exponential stage automatic gain control circuit, an automatic gain control circuit and temperature compensation circuit

摘要

A temperature compensation control circuit to maintain a constant control gain in an AGC (automatic gain control) amplifier. The present invention compensates for the inherent temperature dependence without using any special processing or non-standard device structures. The present invention utilizes the voltage drop across n diodes in series to produce the control voltage difference (V.sub.C -V.sub.C *). These n series diodes are coupled to the collectors of a PNP emitter coupled pair with emitter resistance. This causes the control voltage difference to be dependent on temperature (nkT/q), but this dependency cancels out with the other inherent temperature dependency in the exponential function of the AGC amplifier which is also produced by a diode form. Thus, the present invention provides temperature compensation with minimum component matching problems and without the need for a PTAT (proportional to absolute temperature) current source.