SDAA511 September   2026 OPA192 , PGA855

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Detailed Description
    1. 2.1 ATE Testing Card and Signal Sensing
    2. 2.2 Signal Sensing Requirements
    3. 2.3 Signal Sensing
    4. 2.4 General Purpose Sensing
    5. 2.5 Precision Signal Sensing
      1. 2.5.1 Middle and High Voltage Signal
      2. 2.5.2 Current Signal with Middle and High Common Mode Voltage
      3. 2.5.3 Signal Which Requires Very Low Current Leakage
      4. 2.5.4 Fast Voltage Signal
      5. 2.5.5 Ultra-High Voltage Signal
  6. 3Summary
  7. 4References

2.5.3 Signal Which Requires Very Low Current Leakage

When the current signal range is at the nA or pA level, the current leakage of the sensing path buffer needs to be at the fA level; otherwise, the measuring accuracy will be greatly affected. For fA-leakage op amps, Table 2-3 can be used:

Table 2-3 fA Current Leakage Buffer Amplifiers
PN Key Feature
OPA928 36V, 2.5Mhz, 5V/us, Ib=1fA(typ), CMRR=120dB, THD+N=12ppm, En=1.4uVpp
Offset drift=0.1uV/°C
LMP7721 5.5V, 17Mhz, 10V/us, Ib=3fA(typ), CMRR=100dB, THD+N=7ppm,
Offset drift=1.5uV/°C
LMC608x 15.5V, 1.3Mhz, 1.5V/us, Ib=10fA(typ), CMRR=85dB, THD+N=2000ppm,
Offset drift=1uV/°C