Integrated AF power amps
have seen great improvements in recent years offering improved power
and easier use. The TDA1519C from Philips contains two power amplifiers
providing 11 W per channel stereo or 22 W mono when the two channels are
connected in a bridge conﬁguration. The special in-line SIL9P package
outline allows the chip to be conveniently bolted to a suitable
heatsink. The TDA1519CSP is the SMD version, in this case the heat sink is mounted over, and in contact with, the top surface of the chip.
The operating voltage of this device is from +6V to +17.5V. The two
channels of the amplifier are different in that one channel, between
pins 1 and 4, is a non-inverting amplifier, while the other between pins
9 and 6 is an inverting amplifier. It is therefore necessary in stereo
operation, to wire the speakers so that one of them has its polarity
reversed. Each amplifier has an input impedance of 60kΩ and a voltage
gain of 40dB, i.e. 100 times. When both amplifier are used in a bridge
conﬁguration, the inputs are in parallel so that the input impedance
will be 30kΩ.
A combined mute/standby function is provided on pin 8. In its
simplest form this can be connected to the positive rail via a switch.
When the switch is open the amplifier will be in standby mode and
current consumption is less than 100µA. When the switch is closed, the
amplifier will be operational. A circuit is also shown that uses the
mute input to prevent the annoying switch-on plop heard when power amps
are ﬁrst switched on This is caused by the rush of current to charge
capacitors C1 and C2.
The circuit shown generates a ramp voltage, which is applied to pin
8. At switch on, as the voltage rises from 3.3 V to 6.4 V, the amplifier
will switch out of standby mode and into mute mode allowing C1 and C2
to charge. Only when the ramp voltage on pin 8 reaches 8.5V will the
amplifier switch into active mode. Protection built into the TDA1519C
would seem to make it almost foolproof. The two outputs can be shorted
to either of the supply rails and to each other. A thermal shutdown will
prevent overloading and the power supply input is protected against
accidental reversal of the supply leads up to 6V.