TELEFUNKEN Semiconductors

U4314B

Rev. A1: 26.06.1995

5 (7)

10

30

50

70

90

0

20

40

60

80

120

IF–Input Level ( dB

mV )

110

95 10462

100

+85

°C

+25

°C

–40

°C

0

2040

6080

0

10

20

30

40

70

IF–Input Level ( dB

mV )

100

95 10335

50

60

The following circuit is a mere proposal, how to improve

sensitivity and extend the dynamic range of U4314B to

more than 90 dB. However in most applications the basic

dynamic range of more than 60 dB is sufficient. TEMIC

TELEFUNKEN microelectronic GmbH makes no repre-

sentation that the use of this circuit will not refringe on

existing or future patents and no responsibility for the use

of the information contained herein is assumed. This

circuit is neither optimized concerning tolerances of the

components nor tested versus temperature. It should work

with a single supply voltage of 3 to 12 V. A npn transistor

array CA3045 or similar is used. At least four transistors

are needed to realize two current mirrors and the fifth acts

pensate the quiescent current of the logarithmic

demodulator output and may be replaced by a fixed resis-

tor (typ. 3.3 k

W). The total supply current depends on the

IF-input level and varies between 2 and 7 mA. It is mainly

determined by the current through the PIN diode. We

recommend to use the BA679S PIN diode available from

TEMIC TELEFUNKEN microelectronic GmbH. The

input impedance of this application circuit is approxi-

mately 1.5 k

W || 13 pF.