Power amplifier and its idling current setting circuit
AssigneesNiigata Seimitsu Co., Ltd., Ricoh Company, Ltd.
InventorKazuhisa Ishiguro
Life of this patent
Estimating the term…
Abstract
An idling current setting circuit (3) includes: current setting transistors (Q3, Q4) connected to output transistors (Q1, Q2) in a driver (2) in current mirror form; a plurality of current setting resistors (R1 to R4); and a plurality of switches (ASW1 to ASW4) for switching to any of the current setting resistors (R1 to R4). This enables the idling current to be set by the current mirror ratio between the current setting transistors (Q3, Q4) having no connection with the open gain of the power amplifier and the output transistors (Q1, Q2), so that the idling current can be arbitrarily set independently of the open gain.
Claims3
A power amplifier comprising a pre-driver which amplifies the voltage of an input signal to a desired level;
- a driver which amplifies the power of an output signal of the pre-driver to a desired level;
- and an idling current setting circuit which sets the idling current of the driver:
- the pre-driver includes a differential pair constituted of at least two transistors, and a current mirror circuit for receiving an output of the pre-driver as a single output in double end configuration;
- the driver includes a push pull output transistor connected from a single output point of the pre-driver;
- and
- the idling current setting circuit includes a current setting transistor connected to the output transistor of the driver in current mirror form, a plurality of current setting resistors, a switch for switching to any of the plurality of current setting resistors, and a resistor of a high resistance value connected to a gate of the output transistor.
An idling current setting circuit used in a power amplifier including a pre-driver which amplifies the voltage of an input signal to a desired level and a driver which amplifies the power of an output signal of the pre-driver to a desired level, comprising:
- a current setting transistor connected to the output transistor of the driver in current mirror form;
- a plurality of current setting resistors;
- a switch for switching to any of the plurality of current setting resistors;
- and
- a resistor of a high resistance value connected to a gate of the output transistor.
Dependencies are inferred from the claim text.