Patent ID: 6064256
Filing Date: 2000-05-16
Classification: H03F

Abstract:
A semiconductor device comprising:a first amplifier circuit responsive to a source potential for amplifying an analog signal;a coupling capacitor for blocking a direct-component of an output signal of the first amplifier circuit and transmitting an alternate-current component of the same;a second amplifier circuit responsive to the source potential for amplifying and delivering an output signal of the coupling capacitor;a bias resistor having a first and a second resistance for dividing the source potential, which imposes a first bias potential to the input side of the second amplifier circuit when the first resistance is selected and a second bias potential, which is higher than the first bias potential, when the second resistance is selected;a pad for supplying a test signal in the test operation of the first and second amplifier circuits;a switch circuit connected to the pad for turning on in response to the test signal in the test operation to set the bias resistor to the first resistance and turning off in any non-test mode to set the bias resistor to the second resistance; anda diode connected in parallel to the coupling capacitor for, when the first bias potential is loaded to the input side of the second amplifier circuit, turning on thus to allow the output signal of the first amplifier circuit to bypass the coupling capacitor and run directly to the input of the second amplifier circuit and when the second bias potential is loaded, for remaining turned off.