TDA7350A_05 Datasheet, PDF (13/23 Pages) STMicroelectronics – 22W BRIDGE-STEREO AMPLIFIER FOR CAR RADIO

TDA7350A
of low leakage diodes, too. It guarantees BV_CEO > 20V and BV_CBO > 50V both for NPN and PNP transis-
tors. Basically, the connection shown in fig. 34 has been chosen. First of all because its voltage swing is
rail-to-rail, limited only by the V_CEsat of the output transistors, which are in the range of 0.3Ω each. Then,
the gain VOUT/VIN is greater than unity, approximately 1+R2/R1. (VCC/2 is fixed by an auxiliary amplifier
common to both channel). It is possible, controlling the amount of this local feedback, to force the loop
gain (A . β) to less than unity at frequencies for which the phase shift is 180°. This means that the output
buffer is intrinsically stable and not prone to oscillation.
Figure 34. The New Output Stage
In contrast, with the circuit of fig. 35, the solution adopted to reduce the gain at high frequencies is the use
of an external RC network.
4.8 AMPLIFIER BLOCK DIAGRAM
The block diagram of each voltage amplifier is shown in fig. 36. Regardless of production spread, the cur-
rent in each final stage is kept low, with enough margin on the minimum, below which cross-over distortion
would appear.
Figure 35. A Classical Output Stage
Figure 36. Amplifier Block Diagram
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