PURPOSE: To simplify the circuit constitution to ensure a suited application to formation of the IC by forming the signal intensity detection circuit with no use of the capacitor.

CONSTITUTION: With supply of the intensity displayed signal from signal source 37, differential amplifiers 18∼23 amplify the supplied signals in sequence. And the output signals are supplied to detection output terminals 34 and 35, and the signals obtained by giving the full wave rectification to the intensity displayed signals are detected at the common emitter joints of transistors Q9∼Q20. Accordingly, the cut-off is given sequentially from transistor Q32 toward Q27 with increase of the signals, thus lowering gradually composite collector current it of Q27∼Q32. Then difference current iM between it and colector current i33 of transistor Q33 is supplied to current amplifier 33 to drive signal meter 32 with the swing which is in direct proportion logarithmically to the intensity displayed signals.