Browse Prior Art Database

Differential Input Stage

IP.com Disclosure Number: IPCOM000091077D
Original Publication Date: 1969-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Buckley, F: AUTHOR

Abstract

This amplifier circuit is particularly adapted for monolithic fabrication since it is virtually without resistors or capacitors. Transistors Q1 and Q2 comprise a differential input stage. The emitters of Q1 and Q2 are connected to the collectors of Q3 and Q4. The use of diodes D1...D3 between the base and emitter of Q3...Q5 accurately sets the current output of these transistors. These diodes are preferably fabricated from transistors having a shorted collector-base junction. Q3 and Q4 provide a constant current source for the differential input stage Q1 and Q2.

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 84% of the total text.

Page 1 of 2

Differential Input Stage

This amplifier circuit is particularly adapted for monolithic fabrication since it is virtually without resistors or capacitors. Transistors Q1 and Q2 comprise a differential input stage. The emitters of Q1 and Q2 are connected to the collectors of Q3 and Q4. The use of diodes D1...D3 between the base and emitter of Q3...Q5 accurately sets the current output of these transistors. These diodes are preferably fabricated from transistors having a shorted collector-base junction. Q3 and Q4 provide a constant current source for the differential input stage Q1 and Q2.

The output of constant current source Q3 and Q4 is determined by the value of resistor 1, which sets the current through D1...D3. The voltage drop across these diodes is generated by a current representing i/3, assuming that the diodes conduct equally and the base current to Q3...Q5 is negligible. Since the current density is the same across the parallel connection of D1...D3 and the base emitter diodes Q3...Q5, the collector currents of Q3...Q5 are equal to the currents through D1...D3. Thus m approx. 2i/3 and j approx. i/3. In a negative feedback circuit configuration, transistors Q1, Q2, Q5, and Q6 have equal collector currents since Q1 and Q2 share the current m.

Diode D4 serves as the collector load for Q2. Voltage changes between input terminals 2 and 3 are transformed into current changes by Q1 and Q2 which appear at the collector of Q2. D4 and Q6 act as a current buffer st...