STA7360

Application hints

Doc ID 9814 Rev 4

25/28

6.3

Turn-off

A turn-off pop can occur if the st-by pin goes low with a short time constant. This pop is due

to the fast switch-off of the internal current generator of the amplifier.

If the voltage present across the load becomes rapidly zero (due to the fast switchoff) a

small pop occurs, depending also on Cout, Rload.

The parameters that set the switchoff time constant of the st-by pin are:

●

the st-by capacitor (C4)

●

the SVR capacitor (Csvr)

●

resistors connected from the st-by pin to the logical input (Rext)

6.4

Balanced input in bridge configuration

A helpful characteristic of the STA7360 is that, in bridge configuration, a signal present on

both the input capacitors is amplified by the same amount and it is present in phase at the

outputs, so this signal does not produce effects on the load. The typical value of CMRR is

46 dB.

Looking at Figure 37, we can see that a noise signal from the ground of the power amplifier

to the ground of the hypothetical preamplifier is amplified of a factor equal to the gain of the

amplifier (2 * Gv).

Using a configuration of Figure 38 the same ground noise is present at the output multiplied

by the factor 2 * Gv/200.

This means less distortion, less noise (e.g. motor cassette noise) and/or a simplification of

the layout of PC board.

The only limitation of this balanced input is the maximum amplitude of common-mode

signals (few tens of millivolt) to avoid a loss of output power due to the common-mode signal

on the output, but in a large number of cases this signal is within this range.

Figure 37.

Balanced input in bridge configuration, example 1

Figure 38.

Balanced input in bridge configuration, example 2

Obsolete

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- Obsolete

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