MAT02

–12–

REV. C

current. A set resistor of 549 k

Ω was found to provide the best

step response for this circuit. The resultant supply current is

found from:

V

+

BE

()

(22)

proximately 52

µA which will result in supply current of 784 µA.

Dynamic range of this amplifier is excellent; the OP32 has an

output voltage swing of

±14 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 rais-

ing the collector currents from 1 mA to 3 mA, but power con-

sumption is then increased.

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

~ 3 V). The OP32’s low input offset current, typically less than

1 nA, and low offset voltage of 1 mV cause negligible error

Ω. Since the OP32 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 er-

ror due to finite open-loop gain will be negligible. The OP32

features excellent symmetry of slew-rate and very linear gain.

Signal distortion is minimal.

Frequency compensation is very easy with this circuit; just vary

Gain-bandwidth of the OP32 varies directly with the supply

OUTLINE DIMENSION

Dimensions shown in inches and (mm).

6-Lead Metal Can

(TO-78)

0.250 (6.35) MIN

0.750 (19.05)

0.500 (12.70)

0.185 (4.70)

0.165 (4.19)

REFERENCE PLANE

0.050 (1.27) MAX

0.019 (0.48)

0.016 (0.41)

0.021 (0.53)

0.016 (0.41)

0.045 (1.14)

0.010 (0.25)

0.040 (1.02) MAX

BASE & SEATING PLANE

0.034 (0.86)

0.027 (0.69)

0.045 (1.14)

0.027 (0.69)

0.160 (4.06)

0.110 (2.79)

0.100 (2.54) BSC

5

2

6

4

3

1

0.200

(5.08)

BSC

0.100

(2.54)

BSC

45

° BSC

Figure 23. Fast Logarithmic Amplifier

Figure 24. Low-Noise, Single-Ended X1000 Amplifier