MAT02

–11–

REV. E

Transistors Q2 and Q3 form a 2 mA current source (0.65 V/

330

Ω ~ 2 mA). Each collector of Q1 operates at 1 mA. The

Ω. Since the

OP184 has a minimum open-loop gain of 500,000, total

open-loop gain for the composite amplifier is over 50 million.

Even at closed-loop gain of 1000, the gain error due to finite

open-loop gain will be negligible. The OP184 features excellent

symmetry of slew-rate and very linear gain. Signal distortion is

minimal.

Dynamic range of this amplifier is excellent; the OP184 has an

output voltage swing of

±14.8 V with a ±15 V supply.

Input characteristics are outstanding. The MAT02F has offset

voltage of less than 150

µV at 25°C and a maximum offset drift

of 1

µV/°C. Nulling the offset will further reduce offset drift.

This can be accomplished by slightly unbalancing the collector

load resistors. This adjustment will reduce the drift to less than

0.1

µV/°C.

Input bias current is relatively low due to the high current gain

of the MAT02. The minimum

β of 400 at 1 mA for the

MAT02F implies an input bias current of approximately 2.5

µA.

This circuit should be used with signals having relatively low

source impedance. A high source impedance will degrade offset

and noise performance.

This circuit configuration provides exceptionally low input noise

voltage and low drift. Noise can be reduced even further by

raising the collector currents from 1 mA to 3 mA, but power

consumption is then increased.