EquipmentGaeltec Bridge Amplifier System (GBA)

Ideal for powering and amplifying Gaeltec's Transducers (especially Needles) in the research environment

Mains powered, available with 1, 2, 3, or 4 channels and housed in a convenient rack.

The System is from our parent company's NeuroLog range and uses the low-noise and highly versatile NL109 Bridge Amplifier modules as the main component.

The above picture shows a 3-channel "GBA-3" system.

System contents

  • 1 x NL905 – Rack and Power Supply (Mains power at 115V or 230V a.c.)
  • 1, 2, 3 or 4 x NL109 – Bridge Amplifier Modules
  • 1, 2, 3 or 4 x GSP-026 – single-channel input cables from Gaeltec Transducers to NeuroLog Amplifier
  • 1, 2, 3 or 4 x NL951B-2m – output cables terminated in a BNC plug for your Data Acquisition system
  • Blanking panels, to fill the Rack, as required.

The NeuroLog System – An Overview

The NeuroLog System is now widely accepted throughout the world by scientists who demand high quality, dependability and innovation in their research instrumentation.

Because the NeuroLog System is fully modular, it has the following well recognised advantages over non-modular "multi-purpose" instruments:

  • Greater Flexibility: Complex systems can be quickly assembled or modified.
  • Enhanced Efficiency: Modules can be shared among several set-ups, expanding capabilities without duplication. Only those modules required for a particular task are tied up and occupy rack space.
  • Wider Compatibility: Input and output levels, impedances, connectors, etc., of different modules in the system are compatible, minimizing the problems encountered in interconnecting pieces of equipment of diverse origin.
  • Cost Effective: Only those modules actually required are purchased. You do not pay for all those functions added to an instrument to make it "general purpose". Individual modules can be added to the system at any time, as the scope and orientation of your application changes.

NL905 Compact NeuroLog System Rack & Power Supply (up to 4 modules)

The NL905 is a compact case and power supply unit for the NeuroLog System which is offered for users who require no more than 4 modules for their given application or are short of space. The case measures 130mm (high) x 164mm (wide) x 271mm (deep), has overload protection fuses, a front panel on/off switch, an LED power indicator as well as flip-out feet for bench placement. It is fully compatible with all NeuroLog System modules, either current or discontinued. It is powered by 230 or 115V mains with a rear panel Voltage Selector.

A unique feature of the NeuroLog power supply is a built-in error circuit which indicates (by extinguishing the power supply indicator on the front panel) excessive loading of one or more of the three supply outputs. While it is expected that a power supply failure will never occur using NeuroLog modules, the fault indication is invaluable when testing custom circuits built on the NL50 Blank Module.

The website ( contains a wealth of up to date information on the components of the NeuroLog System as well as downloadable support documents such as specific Application Notes and User's Manuals which can be invaluable when selecting the appropriate modules for a particular application. We are always happy to discuss your requirements if you are unsure what components you require.

The NeuroLog System Modules

The front panel of each module measures 30mm wide by 122mm high. The attached printed circuit board is 152mm long by 102mm high. Each module has a split ring handle attached to its front panel; this serves as a cable run as well as a handle for withdrawing or inserting the module into the case. All module outputs are short circuit proof. The extensive use of standard transistor-transistor logic (TTL) and standard linear integrated circuits ensures the lowest possible cost and highest possible compatibility with other instruments. The output levels and impedances of the linear inputs and outputs are appropriate for general purpose oscilloscopes, low gain chart recorders and data acquisition interfaces. The NeuroLog System is also compatible with the components most frequently used in special circuitry built by individual investigators to meet their own particular needs. Undrilled front panels and special printed circuit boards – assembled as the NL50 Blank Module are available to encourage the design and use of such special purpose modules with the NeuroLog System.

Cables & Accessories

Only micro-miniature coaxial connectors with a "snap-on" action are used in the NeuroLog System, eliminating the nuisances caused by connectors such as the BNC and UHF types which have a "twist-on" or "screw-on" action. All external connections between modules are made through miniature, screened coaxial cable, which reduces cross-talk and transient pick-up.

NL109 Bridge Amplifier

The NL109 BRIDGE AMPLIFIER is a DC coupled, differential amplifier intended for use with transducers which require a bridge excitation voltage such as those manufactured by Gaeltec Devices. The output from the NL109 is the amplified and filtered signal from the Transducer.

The "ZERO" button on each NL109 Amplifier allows each channel to be independently zeroed. This is done by pressing and holding the button for just 1-second. The associated LED indicates when zeroing has been achieved (or failed).

Technical details:


x1 to x5,000


Cal. control provides 0 to -40% gain reduction

High Frequency Cut:

0.3 to 30kHz (±10%)

Low Frequency Cut:

DC, 0.1 or 10Hz


Zero Button with bi-colour LED

Excitation Voltage:

1 to 15V (but MUST be set to 1V for Gaeltec Transducers)

Output Voltage:


Common Mode Rejection Ratio:

>90dB @ 50Hz

Useful information

See our information section for anything from "What a Gaeltec Pressure Transducer is" to "Can I have a Transducer with Double Lumen, Twin Bore, Pig Tail with an Extended Tip?" Click here

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