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ADA400A Differential Preamplifier, Datasheet

ADA400A Datasheet

The ADA400A Differential Preamplifier allows direct oscilloscope measurements of very low amplitude voltages and signals which are not ground referenced. The high impedance of both inputs eliminates the need to add additional ground points in the DUT, thereby avoiding circulating currents which disturb the measurement or the circuit.

Key performance specifications
  • 10 μV/div sensitivity
  • Typically 100 dB CMRR DC to 10 kHz
Key features
  • Active differential preamplifier
  • Integral probe power with TEKPROBE™ BNC
  • The ADA400A is powered directly from TDS400, TDS500, TDS600, TDS700, TDS5000, TDS7000 (TEKPROBE), TDS7000 (TekConnect) w/ TCA-1MEG Series oscilloscopes.
  • The ADA400A may also be powered by a 1103 Probe Power Supply.

  • Mechanical analysis
  • Audio design
  • Biomedical research (not certified for patient connection)
  • Medical equipment (not certified for patient connection)


The high gain and extremely high common mode rejection of the ADA400A Differential Preamplifier provide usable measurements of voltages as low as 5 μV, even in high-noise environments. Selectable bandwidth limiting reduces normal mode noise from digital logic, switch mode power supplies, and line frequency sources. Adjustable differential offset allows the user to null out transducer bridge bias and galvanic potential from the test setup. An "infinite impedance" mode can be selected in the two highest gain ranges allowing accurate measurements of signals with high source impedance.


All specifications are guaranteed unless noted otherwise. All specifications apply to all models unless noted otherwise.

Gain settings
100x, 10x, 1x, 0.1x
≥100,000: 1 DC - 10 kHz


Signal ranges
Gain setting Common Mode signal range Differential signal range 1 Max offset
100x ±10 V 0.1 V ±1.0 V
10x ±10 V 1 V ±1.0 V
1x ±40 V 10 V ±40 V
0.1x ±40 V 80 V ±40 V

1 For higher voltages, attenuating probes may be used, but CMRR performance will be degraded.

Bandwidth limits
100 Hz, 3 kHz, 100 kHz, full (≥1 MHz)
Input impedance
1 MΩ || ~ 55 pF (infinity Ω selectable in 100x and 10x gains)
Typically ≤30 μVRMS at 100x gain (referred to input)

Ordering information


Differential Preamplifier
Standard accessories
Instruction manual
Spare input fuses (2)
Recommended accessories
P6101B 1x passive probe
2 recommended
Service options
Opt. C3
Calibration Service 3 Years
Opt. C5
Calibration Service 5 Years
Opt. D1
Calibration Data Report
Opt. D3
Calibration Data Report 3 Years (with Opt. C3)
Opt. D5
Calibration Data Report 5 Years (with Opt. C5)
Opt. R5
Repair Service 5 Years (including warranty)
Opt. SILV200
Standard warranty extended to 5 years