Browse Prior Art Database

On-Chip Compensation for Operational Amplifiers

IP.com Disclosure Number: IPCOM000039047D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Lobb, KG: AUTHOR [+2]

Abstract

Conventional integrated operational amplifiers use Miller multiplication of an integrated capacitor in the signal path for system stability. The illustrated circuit uses a beta multiplier instead. This technique allows the design and compensation of a fast operational amplifier using only a few components and a small junction capacitor (3 pf). The capacitor multiplier transistor 6 in this circuit is not in the gain path as in conventional Miller amplifiers. The signal path contains only a single voltage gain stage composed of the twin tailed pair 1 and 2, mirrored by diode 3 and transistor '4'. A portion of the signal at 7 passes through the compensation capacitor 8. This current is divided between the base resistor 9 and the base impedance of transistor 6.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

On-Chip Compensation for Operational Amplifiers

Conventional integrated operational amplifiers use Miller multiplication of an integrated capacitor in the signal path for system stability. The illustrated circuit uses a beta multiplier instead. This technique allows the design and compensation of a fast operational amplifier using only a few components and a small junction capacitor (3 pf). The capacitor multiplier transistor 6 in this circuit is not in the gain path as in conventional Miller amplifiers. The signal path contains only a single voltage gain stage composed of the twin tailed pair 1 and 2, mirrored by diode 3 and transistor '4'. A portion of the signal at 7 passes through the compensation capacitor 8. This current is divided between the base resistor 9 and the base impedance of transistor 6. The base current is beta multiplied by 6, and this multiplies the apparent capacitance at 7. By careful design matching of resistors and transistors, an Avol open-loop voltage gain of > 50 DB into 2 kohms, an offset of < 5 mv, a bandwidth > 30 Mhz, and a slew rate > 50 V/usec has been achieved. This design is very useful for book-oriented analog semi-custom (masterslice) designs because of its high performance level using only two transistor sizes and a small component count.

1

Page 2 of 2

2

[This page contains 2 pictures or other non-text objects]