time exhibits drift characteristics of the best low-drift amplifi-

ers The amplifier has been used as a precision pre-amp

DAC where low drift and low noise are both important

for Q2 should be proportional to 1

of Q1A should be about ten times the base current of Q2A

The base current of the output op amp should be no more

than 11000 of the emitter current of Q2 The values of R1

and R2 should be the same as R7

Various formulae for noise

Voltage noise of a transistor per

C

Current noise of a transistor per

Voltage noise of a resistor per

For a more complete analysis of low-noise amplifiers see

AN-222 ‘‘Super Matched Bipolar Transistor Pair Sets New

Standards for Drift and Noise’’ Carl T Nelson

Solid tantalum

Beckman 694-3-R100K-D or similar

TLH8499 – 2

FIGURE 2 New Low-Noise Precision Operational Amplifier as Gain-of-1000 Pre-Amp

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be reasonably expected to cause the failure of the life

failure to perform when properly used in accordance

support device or system or to affect its safety or

with instructions for use provided in the labeling can

effectiveness

be reasonably expected to result in a significant injury

to the user

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