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TDA2557

Dual TV sound demodulator circuits

Philips Electronics 

Philips Semiconductors

Dual TV sound demodulator circuits

Product specification

TDA2555

TDA2557

PARAMETER

SYMBOL

MIN.

TYP.

MAX.

UNIT

AUDIO OUTPUT STAGE

emitter follower with 1,0 mA bias current

DC output voltage

V2,8-14

3,0

4,0

5,0

V

External DC load resistance

R2,8-14

2

−

−

kΩ

AC output current (note 2)

−I2,8-14(p-p)

−

−

0,5

mA

De-emphasis input resistance (note 3) R1,9-14

0,8

1,0

1,2

kΩ

DC voltage (de-emphasis)

V1,9-14

3,7

4,7

5,7

V

Crosstalk attenuation

f = 1 kHz (note 4)

Crosstalk attenuation

α12,21

60

−

−

dB

f = 10 kHz (note 4)

α12,21

60

−

−

dB

Output impedance

R2,8-14

−

25

−

Ω

AF output level (Fig.2, note 5)

MUTE function

Vi(rms) < 60 mV

Switching input current

α

60

−

−

dB

V5-14 = 0 V

V5-14 = VP

Internal d.c. voltage

−I5

−

−

500

µA

I5

−

−

500

µA

no mute (pin 5 not connected)

V5-14

−

6,2

−

V

Notes to the characteristics

1. THD < 0,1% requires a double tuned demodulator circuit (QL = 20). With a single tuned circuit a THD of < 0,5% is

possible (see Fig.1 and Fig.3).

2. If higher a.c. output current is required an external resistor must be applied from output (pins 2 and 8) to ground

(min. 2 kΩ) in order to improve the THD performance (−I2,8 < 4 mA).

3. The de-emphasis time constant is 50 µs.

4.

Crosstalk attenuation is defined as:

o12

=

V-----2---–----1--4---u----n----m-----o----d----u---l--a----t--e----d--

V8 – 14

o21 = V-----8---–----1--4---uV----n2----m–---1--o-4---d----u---l--a----t--e----d--.

5. In the MUTE state the a.f. output level attenuation is more than 60 dB. The MUTE function is only guaranteed for an

r.m.s. value of the input voltage lower than 60 mV. See also Fig.2.

March 1986

6

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