APPLICATION NOTES

Transition time optimization of the MSK 604 follows the same

basic rules as most any other amplifier. Best transition times

will be realized with minumum load capacitance, minimum ex-

ternal feedback resistance and lowest circuit gain. Transition

times will degrade if the output is driven too close to either

supply rail. Feedback and input resistor values will affect tran-

sition time as well. See Figure 1 and Table 1 for recommended

component values.

Figure 1

CURRENT LIMIT

Figure 2 is the recommended active short circuit protection

scheme for the MSK 604. The following formula may be used

for setting current limit:

Current Limit ≈ 0.6V / Rsc

lows:

This formula guarantees that Q2 and Q4 will always have suf-

ficient base current to be in operation. This circuit can be made

tolerant of high frequency output current spikes with the addi-

limit is unnecessary, short pin 7 to pin 8 and pin 11 to pin 12 as

shown in Figure 1.

1KΩ

Ω

Ω

Ω

Ω

499Ω

Ω

Ω

Ω

Ω

402Ω

Ω

Ω

Ω

Ω

-10V/V

-20V/V

-50V/V

0.5-5pF

N/A

N/A

10KΩ

Ω

Ω

Ω

Ω

10KΩ

Ω

Ω

Ω

Ω

20KΩ

Ω

Ω

Ω

Ω

VOLTAGE

GAIN

Table 1

Figure 2

INTERNAL COMPENSATION

Since the MSK 604 is a high voltage amplifier, it is com-

monly used in circuits employing large gains. Therefore, the

internal compensation was chosen for gains of -5V/V or greater.

In circuits running at gains of less than -5V/V, the user can

further compensate the device by adding compensation net-

works at the input or feedback node. Pin 1 (comp) should be

cations.

HIGH VOLTAGE SUPPLIES

The negative high voltage supply on the MSK 604 can be

adjusted to reduce power dissipation. The output of the MSK

rail. Therefore, if the system in question only needs the output

of the amplifier to swing -40V peak, the power supply rails

could be set to -50V safely. For best performance, the mini-

low voltage power supplies should be decoupled as shown in

depending on application requirements.

TRANSITION TIMES

FEED FORWARD TOPOLOGY

The MSK 604 employs a circuit topology known as "feed

forward". This inverting configuration allows the user to real-

ize the excellent D.C. input characteristics of a differential am-

plifier without losing system bandwidth. The incoming signal

is split at the input into it's A.C. and D.C. components. The

D.C. component is allowed to run through the differential am-

plifier where any common mode noise is rejected. The A.C.

component is "fed forward" to the output section through a

very high speed linear amplifier where it is mixed back together

with the D.C. component. The result is an amplifier with most

of the benefits of a differential amplifier without the loss in

system bandwidth.

Rev. B 8/00

3