TS4984 Datasheet, PDF(19/29 Page) STMicroelectronics – 2 x 1W Stereo audio power amplifier with active low standby mode

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TS4984 Datasheet, PDF (19/29 Pages) STMicroelectronics – 2 x 1W Stereo audio power amplifier with active low standby mode

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Application Information

TS4984

4.2 Gain in typical application schematic

The typical application schematic (Figure 64) is shown on page 18.

In the flat region (no Cin effect), the output voltage of the first stage is:

Vou t1 = (âVin) R----R-f--e-i--ne----d-

(V)

For the second stage: Vout2 = -Vout1 (V)

The differential output voltage is:

Vout2 â Vou t1 = 2Vin R----R-f--e--i-ne----d-

(V)

The differential gain, referred to as Gv for greater convenience, is:

Gv = V-----o---u---t--2--V--â--i-n--V----o---u----t--1- = 2R----R-f--e--i-ne----d-

Vout2 is in phase with Vin and Vout1 is phased 180Â° with Vin. This means that the positive terminal of the

loudspeaker should be connected to Vout2 and the negative to Vout1.

4.3 Low and high frequency response

In the low frequency region, Cin starts to have an effect. Cin forms with Rin a high-pass filter with a -3dB

cut-off frequency:

FCL = -2---Ï----R----1-i-n----C----i--n- (Hz)

In the high frequency region, you can limit the bandwidth by adding a capacitor (Cfeed) in parallel with

Rfeed. It forms a low-pass filter with a -3dB cut-off frequency. FCH is in Hz.

FCH = 2----Ï----R-----f--e---e-1--d----C----f--e---e----d- (Hz)

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