SL531
Fig.6 Phase v. input
Fig.7 Transfer characteristics linear plot
Fig.8 Transfer characteristics logarithmic input scale
Fig.9 Circuit diagram 6 stage strip
TYPICAL APPLICATION—6 STAGE LOG STIP
Input log range OdBm to—70dBm
Low level gain 60dB (—70dBm in)
Output dynamic range 20dB
Phase shift (over log range)
±3°
Frequency range 10—200MHz
The circuit shown in Fig 9 is designed to illustrate the use of
the SL531 in a complete strip The supply voltage is fed to each
stage via an external 180
Ω resistor to allow operation to 125°C
ambient If the ambient can be limited to +100
°C then the
internal resistor can be used to reduce the external
component count Interstage coupling is very simple with just
a capacitor to isolate bias levels being necessary.
No
connection is necessary to pin 5 unless operation below
10MHz is required. It is important to provide extra decoupling
on pin 1 of the first stage to prevent positive feedback occuring
down the supply line. An SL560 is used as a unity gain buffer
the output of the log strip being attenuated before the SL560
to give a nominal 0dBm output into 50
Ω.