KH232AM datasheet(4/6 Pages) CADEKA

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DATA SHEET

KH232

REV. 1A January 2004

Operation

The KH232 is based on the current feedback op amp

topology, a design that uses current feedback instead of

the usual voltage feedback.

The use of the KH232 is basically the same as that of the

conventional op amp (see Figures 1 and 2). Since the

device is designed specifically for low gain applications,

the best performance is obtained when the circuit is used

at gains between ±1 and ±5. Additionally, performance is

optimum when a 250

Ω feedback resistor is used.

Figure 1: Recommended non-inverting gain circuit

Figure 2: Recommended inverting gain circuit

Layout Considerations

To assure optimum performance the user should follow

good layout practices which minimize the unwanted

coupling of signals between nodes. During initial bread-

boarding of the circuit use direct point to point wiring,

keeping the lead lengths to less than 0.25”. The use of

solid, unbroken ground plane is helpful. Avoid wire-wrap

type pc boards and methods. Sockets with small, short

pin receptacles may be used with minimal performance

degradation although their use is not recommended.

During pc board layout keep all traces short and direct

The resistive body of Rg should be as close as possible

to pin 5 to minimize capacitance at that point. For the

same reason, remove ground plane from the vicinity of

pins 5 and 6. In other areas, use as much ground plane

as possible on one side of the board. It is especially

important to provide a ground return path for current from

the load resistor to the power supply bypass capacitors.

Ceramic capacitors of 0.01 to 0.1

µf (with short leads)

should be less than 0.15 inches from pins 1 and 9.

Larger tantalum capacitors should be placed within one

inch of these pins. VCC connections to pins 10 and 12

can be made directly from pins 9 and 1, but better supply

rejection and settling time are obtained if they are

separately bypassed as in figures 1 and 2. To prevent

signal distortion caused by reflections from impedance

mismatches, use terminated microstrip or coaxial cable

when the signal must traverse more than a few inches.

Since the pc board forms such an important part of the

circuit, much time can be saved if prototype boards of

any high frequency sections are built and tested early in

the design phase. Evaluation boards designed for either

inverting or non-inverting gains are available.

Offset Voltage Adjustment

If trimming of the input offset voltage (Vos = Vni -Vin) is

desired, a resistor value of 10k

Ω to 1MΩ placed between

pins 8 and 9 will cause Vos to become more negative by

8mV to 0.2mV respectively. Similarly, a resistor placed

between pins 1 and 2 will cause Vos, to become more

positive.

Thermal Considerations

At high ambient temperatures or large internal power

dissipations, heat sinking is required to maintain

acceptable junction temperatures. Use the thermal

model on the previous page to determine junction

temperatures. Many styles of heat sinks are available for

TO-8 packages; the Thermalloy 2240 and 2268 are good

examples. Some heat sinks are the radial fin type which

cover the pc board and may interfere with external

components. An excellent solution to this problem is to

use surface mounted resistors and capacitors.

They

have a very low profile and actually improve high

frequency performance. For use of these heat sinks with

conventional components, a 0.1” high spacer can be inserted

under the TO-8 package to allow sufficient clearance.

Ω

+15V

0.1

3.9

.01

Capactance in

µF

3,7

100

Ω

.01

0.1

3.9

-15V

KH232

Rf = 250Ω

Vin

49.9

Ω

= 1+

250

Ω

+15V

0.1

3.9

.01

Capactance in

µF

3,7

100

Ω

.01

0.1

3.9

-15V

KH232

Rf = 250Ω

For Zin = 50Ω, select

Rg || Ri = 50Ω

100

Ω

Vin

250

Ω

= −

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