LinearAmp signal conditioner amplifier

In our choice there are three different amplifier systems. This page describes the LinearAmp amplifier. Our other amplifier products are BioAmp, and MultiAmp families. All of them are up-to-date, easy to use, highly reliable, microprocessor-controlled constructions. We manufacture three different amplifier families, because the three product lines are optimized for different application fields. Please read through the appropriate descriptions for the details.

LinearAmp amplifier is optimized for high-precision signal conditioning tasks in bioelectrical recording.

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LinearAmp is a programmable amplifier, but it has no sampling circuits in the signal path at all. In other words, it is controlled by a built-in microcontroller, or a remote computer, but it has got only high-performance, low noise, low distortion analogue amplifier circuits. This feature is indispensable when you use averaging techniques for processing its output signal. The internal microcontroller, and the optional digital port (which offers remote control facility from a PC) are optically isolated from the amplifier stages. In this way we could connect all the advantages of high accuracy analogue amplifier circuits, and easy usage of digital control.

Although LinearAmp is a programmable equipment, it does not need a separate computer to work. According to this fact, it can be used as a stand-alone amplifier (while possessing an optional serial port to communicate with a PC). This stand-alone feature is very comfortable, because the computer is always given, but it should be used to collect, and processing the experimental data. LinearAmp's microcontroller on the front panel has got a 3-button keypad, and menu-driven internal software, so it is very friendly to use.

The internal structure of LinearAmp is modular, so the number of the amplifier channels, and the number of the microcontrollers built in one equipment can be decided independently. Only the aspects of the application field should be considered when we decide, how many amplifier channels, and how many microcontrollers will be placed in the cage of the equipment (for example it is comfortable to use only one microcontroller to program all the EEG channels together, but another controller should be used, if there is a single unit channel in the system, and a third controller is necessary, if there are further channels for ECG).

Independently from the number of the microcontrollers, every amplifier channels have got their own DC offset correction circuits, even in a multi-channel system. The voltage range of the offset correction is +/- 200 mV, with 0.1 mV of resolution. In our choice there are two different solutions for the offset correction circuit. One of them is the analogue version with a 10-turn helical potmeter and a digital panelmeter on the front of the equipment. The other version is the digital realisation of the same task: a separated microcontroller, dealing with the numerical control of the offset voltage. The actual version should be specified in the order.

One of the most sophisticated features of LinearAmp is its Low Pass Filter. This circuit is an 8-pole, Bessel-type filter with linear phase response. This special, high quality Low Pass Filter is necessary to realise the anti-aliasing function, which is indispensable before the analogue to digital conversion.

In the LinearAmp the High Pass Filter, the Low Pass Filter, and the Gain have got 8 possible positions. The actual values, realised during the manufacturing process can be ordered with the default parameters, but they can be requested with special values, to meet any special requirements, as well. The default values for the Filter and Gain sections are listed below. Any combination of the parameters can be selected, even the invalid settings (for instance, if the High Pass Filter is set to higher frequency, than the Low Pass Filter). The invalid settings result no faults in the equipment, only the output voltage will be driven to zero.

The Notch Filter (hum noise filter) of the LinearAmp is tuned to 50 Hz (or optionally to 60 Hz). The Notch Filter can be switched on and off in the software running on the microcontrollers. The rejection ratio of the Notch Filter on its central frequency is 40 dB.

There is a possibility to select the full amplifier chain of LinearAmp as Inverting or Noninverting characteristics. This selection is also a menu point of the software running on the microcontrollers.

There is a general Bypass function in LinearAmp. It is also a programmable feature. The Bypass function is not a simple shortcut wire switched between the Input, and the Output connectors of LinearAmp. If the Bypass function is activated, the equipment behaves as a voltage follower, but provides voltage swing limitation for both polarities on the Output. This feature is useful to protect the analogue to digital converter connected to the Output against any faulty input signals appearing on the Input connector of LinearAmp.

If the LinearAmp is used in human experiments, an additional optical isolator circuit should be ordered for every channels with 4 kV of isolation voltage. The optical isolator does not modify any parameter of LinearAmp, because the isolator circuit has got unity gain, with noninverting characteristics.

LinearAmp family is especially powerful in multi-channel applications, since such a level of reliability and flexibility is unthinkable in a usual analogue amplifier. And the top of all that, our amplifier system offers a very reasonable price level in comparison to the number of channels.