Patent ID: 7830210
Filing Date: 2010-11-09
Classification: H03F

Abstract:
1. An amplifier device connected between an electret condenser microphone and a load resistor, the amplifier device comprising: a junction field effect transistor comprising a gate, a source and a drain; a bipolar transistor comprising a base, a high-potential side terminal and a low-potential side terminal; a first resistor comprising a first terminal and a second terminal; and a second resistor comprising a third terminal and a fourth terminal, wherein the gate is connected to a terminal of the electret condenser microphone and the first terminal, the drain is connected to the base, the high-potential side terminal is connected to a terminal of the load resistor, the second terminal is grounded, the source and the low-potential side terminal are connected to the third terminal, the fourth terminal is grounded, and an output voltage is drawn between the high-potential side terminal and the terminal of the load resistor.