BioAmp preamplifier

General description of BioAmp preamplifiers

Preamplifiers are built into separated small cases, because they should be located close to the biological target in the shielded environment. The enclosures of the preamplifiers are always made of metal to provide a good shielding of the sensitive input circuitry.

The actual choice of the preamplifiers and headstages (very small preamplifiers) manufactured in the BioAmp series is quite big. All of them can be built with monopolar (single-ended) inputs or differential (instrumentational) inputs. The available possibilities are:

•  Monopolar (single-ended) preamp choice: 1 - 16 channels
•  Differential ((instrumentational) preamp choice: 1 - 16 channels
•  EEG cable-end version preamp choice: 2 - 24 channels

Until now we have developed many different preamplifier versions for the BioAmp system, including special preamplifiers for user demands. If you can not find the appropriate model for your special task in our actual choice, we will develop a preamplifier especially for you. Our method is, how we improve the features of our BioAmp system, that we collect all the notices, feedbacks and ideas of our customers and we implement their (may be your) knowledge into the features of BioAmp.

The crucial features of the amplifier ICs continuously developed by the semiconductor manufacturers are: noise (signal to noise ratio), offset voltage, offset drift (thermal stability), input bias current, transient response, bandwidth (slew rate). The topologies of the electronic amplifier circuits are similar at the different amplifier manufacturers. The quality of an amplifier is mostly defined by the quality of the first stages. There are no big tricks in the circuitry. The differences of the amplifiers are basically coming from the parameters of the different IC models used in the preamplifiers. Our engineers make huge efforts to study, measure and compare the newest ICs of different semiconductor manufacturers. Supertech Instruments changes the IC models used in the preamplifiers if a better IC model appears on the market. This way we can keep our electronic circuits the best and up-to-date, because always the most sophisticated ICs are implemented in our constructions.

In BioAmp series there are DC and AC preamplifiers. The traditional way - described in the textbooks - how to design an AC amplifier is to place capacitors in series into the signal path. This method works in most cases, but specifically in the biological amplifiers it results long "blackout" periods after spike transients. We employ a tricky circuit topology to keep the baseline by the nominal time constant even in the presence of huge disturbances. The signal path is a true DC amplifier in our AC preamplifiers, too.

General Specifications / Technical Data

We offer the opportunity for our customers to choose the parameters of the preamplifiers freely, optimized for the given task. You can select one of the listed items for every parameter. The choices are:

Gain:

•         10
•         100

Input Impedance:

•         1 MOhm
•         10 MOhm
•         Infinite (approximately 1 TOhm)
•         Any value in the range of 1 kOhm to 10 MOhm

High Pass Filter:

•         1 ms (160 Hz)
•         0.1 sec (1.6 Hz)
•         1 sec (0.16 Hz)
•         2 sec (0.08 Hz)
•         4 sec (0.04 Hz)
•         DC ( 0 Hz)

Fixed (non-changeable) parameters:

•         Bandwidth (upper frequency limit): 20 kHz
•         Supply voltage: +/- 8 to 12 V (symmetrical)
•         Power consumption: 10 mA / channel

BioAmp Main Amplifiers have got universal, multi-purpose connectors for external preamplifiers. This method gives an opportunity to support all the future preamplifier development projects.

BioAmp preamplifier version:

This product is a 1-channel version with differential (instrumentational) input, and without offset correction.

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