3-285

TELCOM SEMICONDUCTOR, INC.

7

6

5

4

3

1

2

8

Figure 4 shows the clamp circuit of a zero-offset com-

parator. Because the clamp circuit requires the inverting

input to follow the input signal, problems with a chopper-

stabilized op amp are avoided. The threshold input must

tolerate the output clamp current

other parts of the system.

Figure 5 shows how the TC7652 can offset-null high

slew-rate and wideband amplifiers.

Mixing the TC7652 with circuits operating at

±15V

requires a lower supply voltage divider with the TC7660

voltage converter circuit operated "backwards." Figure 6

shows an approximate connection.

Figure 6. Splitting +15V With the 7660 at >95% Efficiency

Figure 1. Noninverting Amplifier With Optional Clamp

Figure 2. Inverting Amplifier With Optional Clamp

Figure 5. 1437 Offset-Nulled by TC7652

2

45

3

8

TC

7660

6

10 µF

Ω

1 M

10 µF

+15V

+7.5V

0V

TC7652

+

–

OUTPUT

CLAMP

INPUT

0.1 µF

R2

R1

R3

0.1 µF

OUTPUT

INPUT

R2

R1

CLAMP

0.1 µF

0.1 µF

TC7652

+

–

+

–

+15V

–15V

–7.5V

0.1

µF

IN

OUT

–7.5V

0.1

µF

10 k

Ω

TC7652

741

Some Applications

Figures 1 and 2 show basic inverting and noninverting

amplifier circuits using the output clamping circuit to enhance

overload recovery performance. The only limitations on

replacing other op amps with the TC7652 are supply voltage

(

±8V maximum) and output drive capability (10kΩ load for

full swing). Overcome these limitations with a booster circuit

(Figure 3) to combine output capabilities of the LM741 (or

other standard device) with input capabilities of the TC7652.

These two form a composite device; therefore, when adding

the feedback network, monitor loop gain stability.

Figure 3. Using 741 to Boost Output Drive Capability

+

–

TC7652

OUT

IN

+

–

Ω

22 k

Ω

22 k

FAST

AMPLIFIER

Figure 4. Low Offset Comparator

TC7652

+

–

VOUT

CLAMP

VIN

0.1 µF

0.1 µF

200 k

Ω to 2 MΩ

VTH

LOW NOISE, CHOPPER-STABILIZED

OPERATIONAL AMPLIFIER

TC7652