BTL Mono Amplifier With DC Volume Control

This is BTL  (bridged tied load) mono amplifier with DC volume Control circuit. This circuit uses TDA7052A/AT that is suitable not only for monitors and TV but also battery fed portable radios and recorders. The difference between conventional DC volume circuits and TDA7052A/AT the DC volume control is there is no coupling capacitor is needed in TDA7052A/AT the DC volume control to maintain the low offset voltage. Besides that, the TDA7052A/AT the DC volume control require low supply. The advantages of BTL principle are it has the ripple’s frequency on the supply voltage is twice the signal frequency and the supply current peak is lower. Here is the schematic diagram of the circuit :

To save the cost, a smaller capacitor can be used. The BTL principle can be implemented in portable application that will decrease supply voltage but increases the output power. This amplifier has maximum gain of 35.5 dB. The mute mode is when the DC volume control voltage is below 0.3V. This circuit also equipped with thermal protection. The gain will be decreased when temperature reach +150 C. [Circuit’s schematic diagram source: nxp.com]