Synchronous Amplifier

SKU: SA-01
In stock

Synchronous amplifier for detection of modulated signals in the presence of significant noise.  Compact package and two-button control for quick and easy configuration without compromising performance. Noise contributes negligibly in typical low-noise amplified photodetector (e.g., Eikonal TIA-F-01 and TIA-R-01) applications.

Regular price $642.00 Sale price $642.00

  • Synchronous detection for weak signals
  • Low noise (10 nV/√Hz)
  • Adjustable gain: 20, 40, 60, 80 dB
  • Wide frequency range: 200 Hz–50 kHz
  • Simple, two-button control (gain/phase)
  • Low power, 24 V DC operation
  • TTL-like phase-reference input
  • Compact: 13 mm x 30 mm x 80 mm

  • Detection of chopped signals 
  • Precision AC voltmeter
  • Low noise photodiode backend

Synchronous detection allows measurement of weak signals in the presence of wideband noise (e.g., 1/f or Johnson noise).  By modulating or “chopping” the signal with known phase, the noise can be narrow-banded and shifted to higher frequencies where 1/f noise is insignificant.  The adjacent block diagram shows schematically the principles of operation of the present module.  The inputs to the amplifier are the modulated signal (green) and a square-wave sync reference (red), which has a fixed phase relative to the signal.  The incoming signal is AC-coupled and amplified via the gain stage (blue).  The reference is shifted in phase, 𝝋, to match that of the amplified signal (magenta) and used to route the signal alternately to an inverting and non-inverting input.  The output (cyan) from this stage is a rectified version of the input.  A low-pass filter suppresses the modulation and outputs the rectified signal as the cycle average (orange).  Setting 𝝋 to zero is achieved by adjusting the phase until the output is nulled, then adding an an additional 𝛑/2 phase shift to recover the full signal.

Contact us to discuss custom solutions, pricing and lead-time. Example customizations include:

  • Time constant
  • Gain
  • Operating frequency range


Gain Stage 
Input impedance1 MΩ
Gain settings20, 40, 60 80 dB
Lower 3dB point32 Hz
Upper 3dB point 
    20, 40 dB700 kHz
    60 dB350 kHz
    80 dB50 kHz
Input saturation16 x 10-dB/20 Vpp
Max input voltage±10 V
Reference Phase Control 
Frequency range200 Hz - 50 kHz
Quadrature steps0°, 90°, 180°, 270°
Fine phase range0°–108°
Fine phase step1.08°
Phase reference
VIL: 0-0.9 V
VIH: 2.4-5V
Output Stage 
Settling time (99%)0.83 s
Rolloff12 dB / octave
Output noise70 µV rms (at 80 dB)
Max output voltage9 V (min load: 1.5 kΩ)
Signal connectorsSMA (in, out, ref)
Operating temp5-30° C
24 V DC @ 500 mA
2.5 x 5.5 mm barrel,
positive tip
Aux output power
± 12 V @ 150 mA,
M8 3-pin plug


10 nV Hz-1/2 Equivalent Input Noise

Measured output noise at the 80 dB gain setting as a function of modulation frequency.  The model band spans the range of op amp noise. The gray horizontal line is the 1/f noise contribution from the output filter. The synchronous amplifier will contribute negligibly to the error budget when paired with a typical low-noise transimpedance amplifier.


Auxiliary Output Conveniently Powers Photodetector

Back panel, showing phase reference input, input 24 V power, and ±12 V output power. The ±12 V output is generated entirely from analog (non-switching) components and integrates with the Eikonal amplified photodiode (TIA-F-01). Consistent with the compact profile and two-button interface philosophy, this feature adds further convenience, saving on set-up time and bench space.

High Dynamic Range Optical Density Measurement with a Synchronous Amplifier

In this video, we’ll use a synchronous amplifier (Eikonal SA-01) to make high dynamic range measurements of the transmission of an optical component. We’ll use a modulated laser diode (Eikonal LDFC-01) as a light source, and a large area amplified photodiode (Eikonal TIA-F-01) as the photodetector. In this example, we’ll measure the optical transmission of laser safety glasses. We'll use the Eikonal modules as a system to make measurements sensitive to a part in 10,000.