LM7372

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SNOS926E – MAY 1999 – REVISED MARCH 2013

Op Amp Quiescent Power Dissipation

DC Load Power

AC Load Power

where:

Supply Current

Average Load Current

Average Output Voltage

Table 3 below shows the maximum AC component of the load power dissipated by the op amp for standard

Sinusoidal, Triangular, and Square Waveforms:

Table 3. Normalized maximum AC Power Dissipated in the Output Stage for Standard Waveforms

Sinusoidal

Triangular

Square

amplifier dissipation is the highest for each waveform type. To figure out the AC load current component of

example, with ±5V supplies, a 100

Ω load and triangular output waveform, power dissipation in the output stage is

to the LM7372 junction temperature in the 8-Pin SO PowerPAD package.

POWER SUPPLIES

The LM7372 is fabricated on a high voltage, high speed process. Using high supply voltages ensures adequate

headroom to give low distortion with large signal swings. In Figure 1, a single 24V supply is used. To maximize

the output dynamic range the non-inverting inputs are biased to half supply voltage by the resistive divider R1,

R2. The input signals are AC coupled and the coupling capacitors (C1, C2) can be scaled with the bias resistors

(R3, R4) to form a high pass filter if unwanted coupling from the POTS signal occurs.

Supply decoupling is important at both low and high frequencies. The 10µF Tantalum and 0.1µF Ceramic

associated with the heatsink (Pins 1,8,9 & 16) are at the same potential. Any layout should avoid running input

signal leads close to this ground plane, or unwanted coupling of high frequency supply currents may generate

distortion products.

Although this application shows a single supply, conversion to a split supply is straightforward. The half supply

resistive divider network is eliminated and the bias resistors at the non-inverting inputs are returned to ground,

see Figure 28 (the pin numbers in Figure 28 are given for SO PowerPAD package, those in Figure 1 are for the

SOIC package). With a split supply, note that the ground plane and the heatsink copper must be separate and

are at different potentials, with the heatsink (pin 4 of the SO PowerPAD, pins 6,1,8,9 &16 of the SOIC) now at a

In either configuration, the area under the input pins should be kept clear of copper (whether ground plane

copper or heatsink copper) to avoid parasitic coupling to the inputs.

The LM7372 is stable with non inverting closed loop gains as low as +2. Typical of any voltage feedback

operational amplifier, as the closed loop gain of the LM7372 is increased, there is a corresponding reduction in

the closed loop signal bandwidth. For low distortion performance it is recommended to keep the closed loop

bandwidth at least 10X the highest signal frequency. This is because there is less loop gain (the difference

between the open loop gain and the closed loop gain) available at higher frequencies to reduce harmonic

distortion terms.

Copyright © 1999–2013, Texas Instruments Incorporated

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