Analog Filter/Amplifier Systems

Precision PFA-2

2-Channel Compact
Filter/Amplifier System

High-Performance Signal Conditioning for Low-Level Voltage Inputs in an Economical Package


PFA-2 Two-Channel Compact Filter/Amplifier

Precision quality and performance in an economical benchtop package.

Precision PFA-2 Filter/Amplifier offers 2 channels of high-performance signal conditioning for low-level voltage inputs in an economical benchtop package.

PFA-2 Description

The PFA-2, Precision Filters’ dual-channel filter/amplifier, is compact, rugged, and versatile. Its low-noise, high common-mode rejection balanced differential input with programmable AC/DC input coupling makes the PFA-2 ideal for conditioning static or dynamic signal inputs. Its 6-pole low-pass filters can address applications in the time domain, such as shock measurements, or in the frequency domain, such as spectral analysis or anti-aliasing applications.

Gain is distributed before and after the filter, eliminating out-of-band energy such as transducer resonant peaking, which can clip the amplifier and ruin the data. Front-panel overload detectors warn about pre- and postfilter overload conditions that might otherwise be masked by the filter. The optional 2-pole high-pass filter provides programmable low-frequency roll-off to attenuate sources of low-frequency noise.

PFA-2 Spreadsheet-Style GUI

The PFA-2 is highly programmable via its spreadsheet-style graphical user interface. The GUI controls up to eight PFA-2 units as a single system. Alternatively, you can control the PFA-2 using a high-level command interface via a USB 2.0 connection. Save configurations to the host computer and recall them later. Or save settings to nonvolatile memory for field deployment—no host computer needed.

View the PFA-2 Two-Channel Compact Filter/Amplifier Specification Sheet >


PFA-2 Filter/Amplifier Front Panel

PFA-2 Filter/Amplifier Rear Panel

Innovative Technologies and Features:

Pre-Filter and Post-Filter Gain

The PFA-2 distributes amplifier gain both before and after the filter to provide protection from large out-of-band energy or transients that could cause clipping before the filter, distorting the data. Postfilter gain has resolution of better than 0.025% to enable system scaling of the outputs to match the full-scale input of the external recording device. Overload detectors alert the user to overvoltage conditions.

Flat/Pulse Low-Pass Filter Technology

PFA-2 low-pass filters may operate either in a flat mode, for maximally flat pass-band amplitude response with sharp roll-off, or in a pulse mode, for low phase distortion and optimized transient response. Flat mode provides passband characteristics nearly identical to a Butterworth filter while providing a much sharper roll-off. This mode is a good choice for applications such as spectral analysis. Pulse mode has time-domain response similar to the Bessel filter yet provides superior amplitude response characteristics. Pulse mode is ideal for time-domain applications, including transient (shock) measurements and waveform analysis.

Balanced Differential Input Topology

The PFA-2 Filter/Amplifier input stage is a balanced differential input topology that may be used to receive differential signals from a bridge type transducer or to condition grounded (single-ended) voltage sources without introducing ground loops. The input is versatile in that it has low DC drift for DC measurement applications, low noise for wideband AC measurements and is equipped with programmable AC/DC coupling. AC coupling is useful for eliminating large DC bias on the signal so that more channel gain can be applied in order to emphasize small AC fluctuations in the signal.

PFA-2 Salient Features:

Number of Channels:

  • 2 per system

Input Connectors:

  • Standard: Coaxial BNC’s at front panel
  • Option 1: Twinaxial BNC input

Output Connectors:

  • Individual isolated BNC’s at rear panel


  • Balanced differential input with programmable AC/DC coupling


  • DC coupled, single-ended output, short circuit protected

Test Support:

  • Amplifier Short: A switch at the amplifier input is utilized to ground the input stage for measurement of noise and DC offset.
  • Test Input: Switch disconnects signal from input connector and inject signal on Test Input BNC at the aqmplifier input.

Input Power:

  • 10 to 30 VDC external AC to DC power supply provided with unit

Pre-Filter Gain:

  • x1 to x128 in binary steps

Post-Filter Gain:

  • x1/16 to x16 with 0.025% minimum resolution


  • 4-pole low-pass filters with programmable flat/pulse charateristics
  • Wideband mode: Filter may be removed from the signal path, resulting in 3-pole Butterworth wideband amplifier frequency response with nominal –3 dB frequency at 500 kHz.
  • Optional 2-pole high-pass filter (Option H) for band-pass operation


  • USB remote control with field upgradable firmware
  • Spreadsheet-style GUI interface for control of up to 8 PFA-2 units
  • Nonvolatile memory saves programmed state for field deployment without an attached control computer
  • Input and output overload detection with programmable threshold

Comparison Chart of Precision Filter/Amplifiers Products


PFA-2 Filter/Amplifier PF-1U-FA(High Performance)*

28608B 8-Channel 200 kHz Filter/Amplifiers

28618 8-Channel 200 kHz Filter/Amplifiers

28612 2-Channel 3 MHz Filter/Amplifier

Channels/ Card

2 per system

8 (PF-1U-8FA)
16 (PF-1U-16FA

8 per card

Up to 128

8 per card

Up to 128

2 per card

Up to 32


Balanced differential inputs with programmable AC/DC coupling Balanced differential inputs with programmable AC/DC coupling

Balanced differential inputs with programmable AC/DC coupling

Balanced differential inputs with programmable AC/DC coupling

Programmable single-ended/differential input with programmable AC/DC input coupling (10 hZ or 100 Hz


6-poles; FLAT/PULSE

Optional H; 2-pole High-Pass

4, 8-poles; FLAT/PULSE Low-Pass or 8-Pole Band-Pass

4, 8-poles; FLAT/PULSE
Low-Pass or 8-Pole Band-Pass

4-poles; FLAT/PULSE

6-poles; FLAT/PULSE


Prefilter Gain:
×1 to ×128 in ×2 steps

Postfilter Gain:
×1/16 to ×16 with 0.025% min resolution

Prefilter Gain:
×1 to ×512 in ×2 steps

Postfilter Gain:
×0.25 to ×16 with 0.05% resolution

Prefilter Gain:
×1 to ×512 in ×2 steps

Postfilter Gain:
×1/16 to x16

Prefilter Gain:
×1 to ×64 in ×2 steps

Postfilter Gain:
×1/16 to ×16 in binary steps with vernier adjustment


Prefilter Gain:
x1 to x1000

Out-Band Reserve: Gain is distributed around the filter to accommodate and remove out-of-band signals up to 4x larger than in-band signal of interest without clipping

Cutoff Frequencies

5 Hz to 1.275 kHz in 5 Hz steps

1.5 kHz to 127.5 kHz in
500 Hz steps

Flat Mode:
2 Hz to 2.046 kHz in 2 Hz steps 2.2 kHz to 204.6 kHz in 200 Hz steps and Bypass*

Pulse Mode:
1 Hz to 1.023 kHz in 1Hz steps .1 kHz to 102.3 kHz in 100 Hz steps and Bypass*

2 Hz to 204.6 kHz

1 Hz to 102.3 kHz

FX02: 300 Hz, 1 kHZ, 3 kHz, 10 kHz, 30 kHz*

5 kHz to 315 kHz in 5kHz steps

35 kHz to 3.15 MHz in 50 kHZ steps


DC-coupled, Single-ended DC-coupled, Single-ended

Single-ended with Ground Sense

Single-ended with Ground Sense


* The PF-1U-FA also offers a Standard model. To compare standard and high performance specs for the PF-1U-FA, click here.

** Custom cutoff frequencies are available. Please consult factory..