Title:
COMPLETELY DIFFERENTIAL FILTER FITTED WITH CHANGENER CAPACITOR USING CMOS OPERATION AMPLIFIER NOT HAVING COMMON MODE FEEDBACK
Document Type and Number:
Japanese Patent JPH02219314
Kind Code:
A
Abstract:
PURPOSE: To reduce an area, to reduce power consumption, and to improve a filtering ratio by providing a full differential arithmetic amplifier having two inputs and two outputs, and a pair of feedback circuit respectively having two capacitors and two switches. CONSTITUTION: Two outputs 6 of an arithmetic amplifier 1 are connected through a pair of feedback circuits 8 constituted of capacitors 10 selectively connected between the terminal of a polarization voltage Vp and the terminal of a reference voltage Vr according to the positions of a capacitor 9 and a pair of switches 11 with inputs 2. Then, when each switch 11 is connected with the capacitor 10 side, the capacitor 10 is properly charged with a voltage Vp -Vr and when each switch 11 is connected with the capacitor 9 side, the capacitor 10 is connected in parallel to the capacitor 9. Also, the amplifier 1 is formed of CMOS transistors Tr 13-16 in two systems, and the Tr 16 has a gate connected with each input 2, and an intermediate branch point between the Tr 14 and 15 is connected with each output 6. Thus, an area can be reduced, power consumption can be reduced, and a filtering ratio can be improved.
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Inventors:
NICOLLINI GERMANO (IT)
Application Number:
JP32747889A
Publication Date:
August 31, 1990
Filing Date:
December 19, 1989
Export Citation:
Assignee:
ST MICROELECTRONICS SRL (IT)
International Classes:
H03F3/00; H03H19/00; (IPC1-7): H03H19/00
Domestic Patent References:
| JPS60158708A | 1985-08-20 |
Foreign References:
| EP0293020A1 | 1988-11-30 | |||
| US4609877A | 1986-09-02 | |||
| US4533877A | 1985-08-06 |
Attorney, Agent or Firm:
Shinichi Ogawa (2 outside)