Switching circuit
US4315221A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 25, 1979 |
| Grant date | Feb 9, 1982 |
| Priority date | — |
| Expiry date | Sep 25, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F3/72
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A muting switching circuit for decoupling the output signal from an FM tuner including a transistor PNP-NPN pair push-pull connected between the terminals of a power source with a current mirror circuit supplying bias to the transistor pair in response to an input muting control signal. A middle point potential equal to one-half the voltage of the power source supplying current to the circuit is connected to a common connection point of the transistor pair so that when the transistors are rendered nonconductive by control of the input control signal, the common connection point thereof, which is also the output terminal of the circuit, is brought to the middle point potential immediately so that no pop noise is produced in the output signal. Preferably, a capacitor is coupled between the source of the middle point potential and ground to slow down transitions in the output signal when the power source is switched off or on to thereby prevent pop noise in the output signal at that time.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.