August 1990 4
Philips Semiconductors Product specification
Integrated FM tuner for radio receivers TDA1574T
PINNING
1. Mixer input 1
2. Mixer input 2
3. Wideband information input
4. Ground
5. Voltage reference
6. Oscillator output
7. Oscillator input 1
8. Oscillator input 2
9. Buffered oscillator output
10. Not connected
11. Not connected
12. IF output
13. Standby switch
14. Narrowband information input
15. IF input 1
16. IF input 2
17. Supply voltage
18. Mixer output 1
19. Mixer output 2
20. AGC output Fig.2 Pinning diagram.
FUNCTIONAL DESCRIPTION
Mixer
The mixer circuit uses a double balanced multiplier with a preamplifier (common base input) in order to obtain a large
signal handling range and low oscillator radiation.
Oscillator
The oscillator circuit uses an amplifier with a differential input. Voltage regulation is achieved by utilizing the symmetrical
tan h-transfer-function to obtain low order 2nd harmonics.
Linear IF amplifier
The IF amplifier is a one stage, differential input, wideband amplifier with an output buffer.
Keyed AGC
The AGC processor combines narrow and wideband information via an RF level detector, a comparator and an ANDing
stage. The level dependent current sinking output has an active load which sets the AGC threshold.
The AGC function can either be controlled by a combination of wideband narrowband information (keyed AGC) or by a
wideband/narrowband information only. If narrowband AGC is required pin 3 should be connected to pin 5. If wideband
AGC is required pin 14 should be connected to pin 15.