Sanwa PC20TK - Calculation Problems for Input Circuit

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[6] Calculation Problems for Input Circuit
6-1 Voltage measurement circuit
1. When the input voltage is 1000 V in Fig. 6-1, find R in Ω with which 1 V is obtained as the
standard output (uniform different units of resistance for calculation). Assume that the input
resistance of the LSI connected to the output connector is infinite (
).
2. Circuit using an OP amplifier
In Fig. 6-2, when the input voltage is 500 V, the output voltage is 0.5 V. Find the value for R. As
one of the characteristics of the OP amplifier, the resistance between a and b in Fig. 6-2 is
infinite (
), but the electrical potential difference is 0 (this is called imaginable short).
Fig. 6-1
R kΩ
1 V = • V
990 kΩ + MΩ + R kΩ
500 V Vout
|i| = |i’| hence, =
10 MΩ R
Fig. 6-2
990k£
Input voltage
1000 V
Output voltage
1 V
9 M£
R
10 M£
R
Input voltage
500 V
Output voltage (Vout)
0.5 V
a
b
i
i’