TSH70CD View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TSH70CD' PDF : 33 Pages View PDF
Testing conditions
TSH7x
4.4
Precautions when operating on an asymmetrical supply
The TSH7X 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 (+VCC/2). This bias network must be carefully
designed, in order to reject any noise present on the supply rail.
As the bias current is 15 µA, you must carefully choose the resistance R1 so as not to
introduce an offset mismatch at the amplifier inputs.
Figure 49. Schematic of asymmetrical (single) supply
IN Cin
R1
R2
Vcc+
C3
R3 C1 C2
+
-
R5
Cf
Cout OUT
RL
R4
R1 = 10 kΩ is a typical and convenient value. C1, C2, C3 are bypass capacitors that filter
perturbations on VCC, as well as for the input and output signals. We choose C1 = 100 nF
and C2 = C3 = 100 µF.
R2, R3 are such that the current through them must be greater than 100 times the bias
current. Therefore, we set R2 = R3 = 4.7 kΩ.
Cin, as Cout, is chosen to filter the DC signal by the low-pass filters (R1,Cin and Rout, Cout).
By taking R1 = 10 kΩ, RL = 150 Ω, and Cin = 2 µF, Cout = 220 µF we provide a cut-off
frequency below 10 Hz.
Figure 50. Use of the TSH7x in gain = -1 configuration
Cf
IN Cin
1k
1k
-
R1
Vcc+
+
R2
C3
R3 C1 C2
Cout OUT
RL
Some precautions must be taken, especially for low-power supply applications.
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