TDA7294S

6/16

(*) R1 = R3 for pop optimization

(**) Closed Loop Gain has to be

≥ 26dB

(***) Multiply this value for the number of modular part connected

Note:

If in the application, the speakers are connected via long wires, it is a good rule to add between the output

and GND, a Boucherot Cell, in order to avoid dangerous spurious oscillations when the speakers terminal

are shorted. The suggested Boucherot Resistor is 3.9

Ω/2W and the capacitor is 1µF.

4

Introduction

In consumer electronics, an increasing demand has arisen for very high power monolithic audio amplifiers

able to match, with a low cost, the performance obtained from the best discrete designs.

The task of realizing this linear integrated circuit in conventional bipolar technology is made extremely dif-

er devices, and, as a consequence, the maximum attainable output power, especially in presence of highly

reactive loads. Moreover, full exploitation of the SOA translates into a substantial increase in circuit and

layout complexity due to the need of sophisticated protection circuits.

To overcome these substantial drawbacks, the use of power MOS devices, which are immune from sec-

ondary breakdown is highly desirable. The device described has therefore been developed in a mixed bi-

polar-MOS high voltage technology called BCDII 100.

4.1 Output Stage

The main design task in developping a power operational amplifier, independently of the technology used,

is that of realization of the output stage. The solution shown as a principle shematic by Fig.5 represents

the DMOS unity - gain output buffer of the TDA7294S.

COMPONENTS

SUGGESTED

VALUE

PURPOSE

LARGER THAN

SUGGESTED

SMALLER THAN

SUGGESTED

C4

10

µFST-BY TIME

CONSTANT

LARGER ST-BY

ON/OFF TIME

SMALLER ST-BY ON/

ON/OFF TIME;

POP NOISE

C5

22

µFXN (***)

BOOTSTRAPPING

SIGNAL

DEGRADATION AT

LOW FREQUENCY

C6, C8

1000

µFSUPPLY VOLTAGE

BYPASS

C7, C9

0.1

µFSUPPLY VOLTAGE

BYPASS

DANGER OF

OSCILLATION

Table 6. Application Suggestions (continued)

MASTER

UNDEFINED

SLAVE

D98AU821