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Differential Amplifier

IP.com Disclosure Number: IPCOM000092315D
Original Publication Date: 1968-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Liu, CC: AUTHOR

Abstract

This circuit compensates differential amplifiers for gain variation with respect to operating temperature. Differential amplifier 10 has transistors 12 and 20 having common coupling between emitters 16 and 24. Voltage source 36 is connected through resistors 38 and 42 to collectors 18 and 26 of the transistors. Differential input signals E1i and E2i are applied to the bases of transistors 12 and 20 at terminals 28 and 32. Differential output signals appear at terminals 40 and 44. Transistor 46 provides a current source for transistors 12 and 20. Base 48 of transistor 46 is coupled through resistor 60 to a reference potential. Emitter 50 is connected to a negative voltage source 62 through resistor 54. Transistor 46 has a controlling bias voltage Vs which is the potential difference between voltage source 62 and base 48.

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Differential Amplifier

This circuit compensates differential amplifiers for gain variation with respect to operating temperature. Differential amplifier 10 has transistors 12 and 20 having common coupling between emitters 16 and 24. Voltage source 36 is connected through resistors 38 and 42 to collectors 18 and 26 of the transistors. Differential input signals E1i and E2i are applied to the bases of transistors 12 and 20 at terminals 28 and 32. Differential output signals appear at terminals 40 and 44. Transistor 46 provides a current source for transistors 12 and 20. Base 48 of transistor 46 is coupled through resistor 60 to a reference potential. Emitter 50 is connected to a negative voltage source 62 through resistor 54. Transistor 46 has a controlling bias voltage Vs which is the potential difference between voltage source 62 and base 48. The value of bias voltage is established by the basic equation Vs = (R-1)KT/q+Vg. R is a constant for the particular semiconductor of transistor current source. K is Boltzman's constant. T is absolute temperature in degrees Kelvin. The charge on an electron is q. Vg is the energy gap for the particular semiconductor of transistor current source. An amplifier gain free from changes in temperature is realized.

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