Charging circuit and/or discharge circuit and carrier detection circuit using them

Abstract

A charge / discharge circuit creates a carrier detection level based on a received signal in a carrier detector circuit for detecting the presence or absence of a carrier in such applications as a receiver for an IR remote controller. The charge / discharge circuit operates to amplify a current, that is produced in N-type transistors QN1, QN2, QN3 and a reference current source, in a P-type transistor QP1. The amplified current is mirrored by a current mirror circuit to be supplied as an emitter current of a P-type transistor QP2. The charge / discharge circuit charges a capacitor with a small current, i.e., a base current of the P-type transistor QP2. The charge / discharge circuit includes a bias voltage source which produces such a bias voltage that the emitter-collector voltage of the P-type transistor QP1 becomes substantially equal to the emitter-collector voltage of the P-type transistor QP2. As a result, it is possible to limit an error of a charge current charged into the capacitor, which is caused by the emitter-collector voltage dependent change of the collector current and thus the base current, known as the Early effect.

Description

technical field [0001] The present invention relates to a charging and discharging circuit for charging or discharging at least one of capacitors with a fixed current, and a carrier detection circuit using the circuit, which is used for so-called infrared remote control receivers and resolution of signals including carrier waves. Tuner, etc., to form the carrier detection level. Background technique [0002] The infrared remote control receiver is developing toward miniaturization, and can be composed of two chips in which an external photodiode is connected to an IC chip. Therefore, a capacitor that is charged / discharged with or without carrier detection and whose output voltage is at the carrier detection level is required to maintain a small charge and discharge current with high precision as a micro capacitor that can be incorporated in the IC chip. [0003] FIG. 5 is a block diagram showing an example of the configuration of the infrared remote control receiver 1, and ...

AI Technical Summary

Problems solved by technology

In consideration of the Early effect, in order to form an acceptable duty within the specification range, the duty ratio is set high, which makes it difficult to separate the noise and the carrier wave of the fluorescent lamp starter, resulting in unacceptable and erroneous operation. The main reason

Images