Signal amplifiers are electronic devices that receive and amplify signals for processing or digitization. They produce only a small amount of internal noise and increase signal strength by a significant factor. Signal amplifiers often include field-effect and bipolar junction transistors, electronic components that amplify signals without producing significant amounts of thermal noise. They also include one or more operational amplifiers. Signal inputs include AC and DC voltages, AC and DC currents, charges from piezoelectric devices, and frequencies and other specialized waveforms. Some signal amplifiers receive inputs from accelerometers, thermocouples, thermistors, resistance temperature detectors (RDTs), strain gauges, or bridges. Other devices receive signals from linear rotary differential transformers (LVDTs) and rotary variable differential transformers (RVDTs).

Device Specifications

Device specifications for signal amplifiers include the number of analog channels and the number of differential channels. When single-ended outputs are available, suppliers often specify the maximum number of analog channel outputs as twice the number of differential outputs. Differential channels, which have two inputs, define the voltage as the signal to process between the two inputs. Other device specifications for signal amplifiers include maximum output voltage, gain range, bandwidth, and input impedance. Gain, the factor by which input signals are multiplied, is frequently greater than unity; however, gain can be fractional when a reduction (attenuation) of signal amplitude is desired. Bandwidth, the difference between the high and low limits of the frequency response, is a measurement that is typically defined by a variation from a nominal value by a stated value such as 3 dB. Impedance, the resistance to alternating signal flow, is a result of the resistance, capacitance, and inductance of a device’s circuitry. For signal amplifiers, input impedance is typically specified as much greater than the impedance of the devices whose signals are amplified.  

Filter and Amplifier Specifications

Signal amplifiers vary in terms of filter and amplifier specifications. Devices that include integral filters allow some signal frequencies to pass while attenuating others. Sample-and-hold amplifiers quantize signal samples to discrete levels, provide programmable triggers, and conform to system timing parameters. Isolation amplifiers are designed to isolate high DC levels while passing relatively small differential signals. Since amplifier gains or multiplication factors may be greater than one or only fractional, programmable gain amplifiers are also available. These devices allow users to make adjustments from a local interface such as a front panel, or from a computer interface, touch screen, or remote handheld device. Some signal amplifiers are programmable, networkable, web-enabled, or bundled with application software for controlling or monitoring data acquisition or signal conditioning from a supervisory or host computer.

Form Factors

There are a variety of form factors for signal amplifiers. Some devices mount on integrated circuits (ICs), standard DIN rails, or printed circuit boards (PCBs) that attach to enclosures or plug into computer backplanes. Others bolt into walls, cabinets, enclosures, or panels. Rack-mounted units fit inside a standard 19” telecommunications rack. Modular styles include stackable units that dock in bays, slots, or boxes. Benchtop or freestanding signal amplifiers often feature full casings or cabinets and integral interfaces.

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