APPLICATION NOTES

HEAT SINKING

To determine if a heat sink is necessary for your application

and if so, what type, refer to the thermal model and governing

equation below.

COMPENSATION

The MSK 032, can be frequency compensated by connecting

an R-C snubber circuit from pin 3 to pin 4 as shown below.

POWER SUPPLY BYPASSING

The recommended capacitor value is 0.01µF and the resis-

tor value can range from 2

Ω to 500Ω. The effects of this R-C

snubber can be seen on the typical performance curve labeled

trates the decrease in transition time as snubber resistance in-

creases. This occurs because the high frequency components

of the input square wave are above the corner frequency of the

R-C snubber and are applied common mode to the bases of the

second differential pair, (pins 3 and 4). There is no differential

gain for these higher frequencies since the input signal is ap-

plied common mode. Without the high frequency components

appearing at the output, the slew rate and bandwidth of the op-

amp are limited. However, at the cost of speed and bandwidth

the user gains circuit stability. A good design rule to follow is: as

closed loop gain decreases, circuit stability decreases, therefore

snubber resistance should decrease to maintain stability and avoid

oscillation. The MSK 032 can also be compensated using the

standard LH0032 techniques.

Where

Governing Equation:

Conditions:

Vcc=±16VDC

Vo=±8Vp Sine Wave, Freq.= 1KHz

Ω

For a worst case analysis we treat the +8Vp sine wave as an 8

VDC output voltage.

1.) Find driver power dissipation

Rev. C 9/06

3

Example:

This example demonstrates a worst case analysis for the op-

amp output stage. This occurs when the output voltage is 1/2

the power supply voltage. Under this condition, maximum power

transfer occurs and the output is under maximum stress.

= (16V - 8V) (8V/510Ω)

===== 125.5mW

4.) R

5.) R

6.) Rearrange governing equation to solve for R

R

= ((125°C-100°C) /0.13W) - 187° C/W - 0.15°C/W

= 192.3 - 187.15

= 5.2°C/W

The heat sink in this example must have a thermal resistance

of no more than 5.2°C/W to maintain a junction temperature

of no more than+125°C.

SLEW RATE

SR = 2

response of the amplifier and is calculated from the full power

bandwidth frequency.

SLEW RATE LIMIT

dv/dt: The slew rate limit is based upon the amplifier's res-

ponse to a step input and is measured between 10% and 90%.

RL=510

Ω

Both the negative and positive power supplies must be

effectively decoupled with a high and low frequency bypass

circuit to avoid power supply induced oscillation. An effective

decoupling scheme consists of a 0.1 microfarad ceramic capa-

citor in parallel with a 4.7 microfarad tantalum capacitor from

each power supply pin to ground.

Thermal Model: