Data Sheet

Precautions on asymmetrical supply operation TSH80, TSH81, TSH82, TSH84
22/30 DocID009413 Rev 9
5 Precautions on asymmetrical supply operation
The TSH8x device can be used with either a dual or a single supply. If a single supply is
used, the inputs are biased to the mid-supply voltage (+V
CC
/2). This bias network must be
carefully designed so as to reject any noise present on the supply rail.
As the bias current is 15 µA, use a high resistance R1 (approximately 10 kΩ) to avoid
introducing an offset mismatch at the amplifier’s inputs.
Figure 34. Asymmetrical supply schematic diagram
C1, C2, C3 are bypass capacitors intended to filter perturbations from V
CC
. The following
capacitor values are appropriate:
C1 = 100 nF and C2 = C3 = 100 µF
R2 and R3 are such that the current running through them must be superior to 100 times the
bias current.
Therefore, use the following resistance values:
R2 = R3 = 4.7 kΩ
C
in
and C
out
are chosen to filter the DC signal by the low-pass filters (R1, C
in
) and
(R
out
, C
out
). With R1 = 10 kΩ, R
out
= R
L
= 150 Ω, and C
in
= 2 µF, C
out
= 220 µF the cutoff
frequency obtained is lower than 10
Hz.
Figure 35. Use of the TSH8x in a gain = -1 configuration
IN
R1
OUT
R2
R3
C1
C3
+
-
R4
C2
R5
Cf
RL
Cin
Cout
AM00845
Vcc+
IN
R1
OUT
R2
R3
C1
C3
+
-
C2
AM00846