AN2653 datasheet(16/22 Pages) STMICROELECTRONICS

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Snubber network compensation method

AN2653

16/22

Snubber network compensation method

5.1

Theoretical overview

Figure 25 shows another way to stabilize an operational amplifier driving a capacitive load.

The snubber network compensation method consists in adding an RC series circuit

connected between the output and the ground. It is particularly recommended for lower

voltage applications, where the full output swing is needed.

Introducing a second load resistor RSN in the circuit decreases the resistive load, and as a

result, pushes the pole caused by the capacitive load to higher frequencies, from

Therefore, stability is increased.

Furthermore, adding a serial capacitor CSN with RSN removes the impact of RSN in DC.

On one hand, CSN must be big enough to consider that its impedance is small compared to

RSN at the frequencies where RSN plays its role of stabilizer.

On the other hand, RSN being very small, CSN must be small enough because when the

frequency increases, the system becomes limited by the current flowing through RSN and

CSN (depending on the output voltage swing).

Therefore, in the following examples, CSN is limited to 100 nF in order to not limit the

frequency range.

Figure 25.

Snubber network schematics

Figure 26.

Snubber network equivalent

schematics for loop gain

calculation

()C

⋅

------------------------------------------------

()C

⋅

---------------------------------------------------------------------

SNω

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–

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AN2653 Datasheet(PDF) 16 Page - STMicroelectronics