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 Lecture for Measurement

Posted 2020/5/20

Measurement of Small AC Signals Superimposed on Large DC Signals

Preamplifier with DC Signal Removal and Low Noise

1. Protection from Large Signals

Measuring a small AC signal superimposed on a large DC signal requires a preamplifier that could not only remove DC voltage but also maintain low noise. The preamplifier "CMP61102" is a product that satisfies both of these requirements. (Figure 2.) The protection circuit that can input a DC signal of 40V or 80V protects the amplifier from damage caused by large voltage. Electrical Characteristics are shown in Table 2.

Figure 2. Preamplifier for measuring small AC signals superimposed on large DC signals

Table 2. Electrical Characteristics

Description Electrical Characteristics
Maximum Input Voltage ±40 V
*Extension to ±80 V is possible
Input Impedance 100 kΩ
Voltage Gain 60 dB
Equivalent Input Noise Voltage Density 2 nV/√Hz or less
Upper Cutoff Frequency 3 MHz
LPF Switching Function
(Upper cutoff frequency setting values)
7 levels switchable via a rotary switch
10, 100, 1k, 10k, 100k, 1MHz, THRU
Lower Cutoff Frequency 1 Hz
*can be extended to 0.1 Hz or less
Maximum Output Voltage ±10 V

*Please contact us in advance for customized products.


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