TS925AI(2011) View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

TS925AI
(Rev.:2011)

Rail-to-rail high output current quad operational amplifiers with standby mode and adjustable phantom ground

STMicroelectronics 

TS925

3.1

Using the TS925 as a preamplifier and speaker driver

Preamplifier configuration

The operators A1 and A4 are wired with a non-inverting gain of respectively:

● A1# (R4/(R3+R17))

● A4# R6/R5

With the following values:

● R4 = 22 kΩ - R3 = 50 Ω - R17 = 1.2 kΩ

● R6 = 47 kΩ - R5 = 1.2 kΩ,

The gain of the preamplifier chain is therefore equal to 58 dB.

Alternatively, the gain of A1 can be adjusted by choosing a JFET transistor Q1 instead of

R17. This JFET voltage controlled resistor arrangement forms an automatic level control

(ALC) circuit, useful in many microphone preamplifier applications. The mean rectified peak

level of the output signal envelope is used to control the preamplifier gain.

3.2

Headphone amplifier

The operators A2 and A3 are organized in a push-pull configuration with a gain of 5. The

stereo inputs can be connected to a CD player and the TS925 can directly drive the head-

phone speakers. This configuration shows the ability of the circuit to drive a 32 Ω load with a

maximum output swing and high fidelity suitable for sound and music.

Figure 19 shows the available signal swing at the headset outputs: two other rail-to-rail

competitor parts are employed in the same circuit for comparison (note the much-reduced

clipping level and crossover distortion).

Doc ID 4949 Rev 4

11/18

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