Engineering Creativity for Neuroscience
BioAmp DC Universal Biological Amplifier System V.7
- they are general purpose biological amplifiers, optimal for all electrophysiological applications. Most of the competitor amplifiers are not able to record DC potentials. BioAmp has got DC recording capability. In other words one of its high pass filter positions is 0 Hz. Furthermore there are precision offset voltage correction modules (analog and digital) as orderable options. BioAmp system can be configured 1 to many channels modularly.
An example: 4-channel BioAmp. Click on the picture to get it in full size
BioAmp's Main Fields of Applications
- Extracellular recording
- Microelectrode recording (Single-unit activity, Juxtacellular recording, Field Potential, Motor Units, etc.)
- Multi-channel DC recording in epilepsy research
- Evoked Potentials in the brain (EVP)
- Body-surface potentials (ECG, EMG, EEG, ERG, etc.)
- Heart micropotentials (HIS-bundle, Late Potential, etc.)
- Multi-channel applications (EEG Brain Mapping, Cortical Depth Mapping, etc.)
BioAmp 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. One can say, that it is old fashioned. We keep this traditional construction style, because it provides supreme accuracy and unsurpassable linearity. This full-analog feature is indispensable when you use averaging techniques for processing its output signal. The internal Amplifier Setup Controller and the optional digital port (which offers remote control facility from a PC) are optically isolated from the amplifier stages. This way we could connect all the advantages of high accuracy analogue amplifier circuits and easy usage of digital control.
Although BioAmp is 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 to process the experimental data. Every Amplifier Setup Controller on the front panel has got a 3-button keypad and menu-driven internal firmware, so it is very friendly to use.
The internal structure of BioAmp is modular, so the number of the amplifier channels and the number of the Amplifier Setup Controllers built in the 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 Amplifier Setup Controllers will be placed in the equipment cage (for example it is comfortable to use only one Amplifier Setup Controller to program all the EEG channels together, but another Amplifier Setup Controller should be used if there is a single unit channel in the system, and a third Amplifier Setup Controller is necessary, if there are further channels for ECG). The front plate Amplifier Setup Controller drives an internal serial bus. On this bus the Amplifier Setup Controller is the master and the amplifier boards are the slaves. The slaves cannot be addressed on the bus. All slaves that are connected to the bus receive the commands from the master at the same time. An Amplifier Setup Controller can drive any number of amplifier boards. The slaves are wired on the bus on a fixed way. This is the reason, why usually more than one Controller is located on the front plate. Examples: a 16-channel equipment can be designed with three Amplifier Setup Controllers on the front: Arrangement (1): channels 1 to 8 are connected to the 1st Controller, channels 9 to 12 are connected to the 2nd Controller and channels 13 to 16 are connected to the 3rd Controller. Arrangement (2): channels 1 to 12 are connected to the 1st Controller, channels 13 to 15 are connected to the 2nd Controller and only channel 16 is connected to the 3rd Controller. Other convenient arrangements can be created, too.
BioAmp amplifier system offers a very reasonable price level in comparison to the number of channels.
Picture Gallery of a Few Different BioAmp Main Amplifiers
Click on the picture to get it in full size
Single-channel basic model Single-channel DC model with offset voltage controller
Dual-channel task-specific model, evoked potential analyzer 4-channel model
8-channel basic model 8-channel DC model ... with its preamplifier
16-channel model ... its internal looking, the PCBs of channels 1 to 8
Specifications / Technical Data
In the BioAmp system there are 8 positions of gain, 8 positions of high pass filter and 8 position of low pass filter in the menu to choose from. The actual values, what should be realized 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.
|High Pass Filter||Low Pass Filter||Gain|
|DC (0 Hz)||15 Hz||500|
|0.16 Hz (1 s)||30 Hz||1,000|
|0.53 Hz (0.3 s)||70 Hz||2,000|
|1.6 Hz (0.1 s)||150 Hz||5,000|
|5.3 Hz (0.03 s)||500 Hz||10,000|
|10 Hz||2 kHz||20,000|
|30 Hz||5 kHz||50,000|
|100 Hz||10 kHz||100,000|
There is a possibility to select the full amplifier chain of BioAmp as Inverting or Noninverting characteristics. This selection is also a menu point of the firmware running on the Amplifier Setup Controller.
Offset voltage arisen on the recording electrodes can be corrected on three different ways, depending on the actual amplifier model. All the below mentioned voltages are referring to the input of the preamplifier (in other words referring to the electrode).
- Analog offset voltage correction in the Preamplifier:
Offset voltage correction range: +/- 700 mV
Control method: 10-turn helical potentiometers
It can be built into the Monopolar (single-ended) preamplifiers only
- Digital offset voltage correction in the Main Amplifier:
Offset voltage correction range: +/- 200 mV
Resolution: 100 microVolts
Control method: Digital Offset Voltage Controller unit
- The above two methods combined together:
Coarse offset voltage correction in the preamplifier
Fine digital offset voltage correction in the Main Amplifier
BioAmp DC is an extremely versatile construction. Before ordering your amplifier, please consult with our development engineer to find the optimal and most comfortable offset correction method for your given signal recording paradigm.
Digital Offset Voltage Controller
This unit is an orderable part of the BioAmp DC amplifier models. It is a dedicated microcontroller with its own LCD display, built on the front plate of the Main Amplifier.
Number of channels: 16 (it can be used in amplifier models of 1 to 16 channels)
Offset voltage correction range (referring to the electrode): +/- 200 mV
Resolution: 100 microVolts
The noise level of BioAmp was measured under the following conditions. A monopolar (single-ended) headstage was used. The input signal of the headstage was generated by a battery-powered square wave generator. The output impedance of this generator was 470 Ohms. The measured noise voltages were referring to the input of the headstage (in other words, they were measured at the output, but they were calculated to the input, divided by the actual gain). The actual settings of the BioAmp Main Amplifier, except the low pass filter, have negligible effect for the total noise characteristics. The noise level depends mainly on the type of the preamplifier and the low pass filter setting. The results of the noise measurement are:
If the bandwidth is 10 kHz (the low pass filter is opened to the widest range), the input noise RMS voltage is less than 12 microVolts (50 microVolts peak-to-peak).
If the bandwidth is limited to 2 kHz with the low pass filter, the input noise RMS voltage is less than 5 microVolts (20 microVolts peak-to-peak).
If the bandwidth is limited to 500 Hz with the low pass filter, the input noise RMS voltage is less than 2.5 microVolts (10 microVolts peak-to-peak).
The difference between amplifier models mostly depends on the quality of the design. Such features as hum noise, square wave transient response, phase response, frequency domain characteristics, ability of parasite oscillations, thermal stability, reliability, etc. are responsibility of the designer. But there is no real difference in the signal to noise ratios of biological amplifiers manufactured by different firms. The signal to noise ratio depends on the internal design of the amplifier integrated circuits. The race of the smaller electronic noise is a race of the semiconductor manufacturers. The designer can choose the best amplifier ICs of the leader semiconductor factories.
There is a general design method in the high gain amplifiers, what is applied in BioAmp, as well. Usually in the biological amplifiers, as in our amplifiers, too (if optical isolators are not used) the Input GND and Output GND points are connected together internally. The resistance between them is less than 0.05 Ohms. However they are signed as different points, because in the interior of the amplifier the ground network forms a linear topology, not a single-point GND (as it is advised in the text-books). The suppression of the hum noise is better if the ground line follows the signal line linearly according to the increasing signal amplitudes from the input to the output. To establish a single-point shielding ground is a good solution at the output end of the signal ground line. Unfortunately the security ground wires are also connected to the metal enclosures of the equipments. The security ground wires are usually hum noise sources for the biological amplifiers (because they usually drive some mains-frequency fault currents from other equipments, from other rooms), but they must not be disconnected, they are compulsory to be used. If you use a mains isolation transformer with symmetrical secondary coil, you can eliminate the disadvantage of the security ground (if in your lab it is allowed to use, please check the local rules). The vibration isolation table, the manipulators, the Faraday-cage, metal parts in the Faraday-cage, the oscilloscope, the PC, the Output GND of the amplifier and the real, separated signal ground line (coming from the earth directly, if it is available) should be connected to this single-point shielding ground. But the ground point of the biological target (the slice chamber or the body of the animal) should be isolated from the shielding ground point (special care should be taken with the metal parts close to the target in the Faraday-cage). The Input GND point of the amplifier is used to provide a low impedance ground to the biological object only. The Input GND point to the biological object is the GND pin at the input of the headstage.
The BioAmp system must not be used in human experiments, because it has no European permission for human applications.
The complete User Manual of the BioAmp amplifier system is available for download.
The Downloadable pin assignment of the 20-pin, 2.54 mm output wire connector of each 8-channel output sections of the BioAmp amplifier is available.
Preamplifiers (in other words Headstages)
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 by Supertech Instruments 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, what are 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.
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.
Picture Gallery of a Few Different Preamplifiers
Click on the picture to get it in full size
Single-channel monopolar preamplifier (moveable by micromanipulator)
4-channel monopolar 4-channel differential ... together
8-channel DC preamplifier top looking ... and its front looking
16-channel custom designed preamplifier prototype
Accessories for Microelectrode Amplifiers
BioAmp system has got an optional optical isolator module, what can be configured for the same channel number as the whole amplifier. The optical isolator module has got 2.5 kV of isolation voltage. The optical isolator module does not modify the technical data of the base amplifier except one parameter. The high pass filter can not be used with DC setting if the optical isolator module is implemented. The optical isolator module provides an exceptionally high level of hum noise suppression. It meets the requirements of the standard industrial isolation level, but it does not provide a legal patient security for human experiments.
Mains isolation transformers with symmetrical secondary coils can efficiently reduce the hum noise level of the amplifiers supplied from such transformers. In our product choice there is a 1 kVA toroidal isolation transformer. It is built in a strong aluminum enclosure with many mains sockets on it. It has got a built-in residual current device and soft start circuit.
Unit Spike Detector (Action Potential Level Discriminator) seems to be an old fashioned circuit, but it is very useful in some cases. It can substitute a difficult and expensive data analysis hardware and software systems in such applications where the distribution of the action potential spikes should be processed.
Special and Unique Amplifiers for Biology
On the one hand our BioAmp amplifiers are extremely versatile biological amplifiers. They can manage every signal recording task in the life science. On the other hand our design engineers have several decades of experience in the field of amplifier design for biology. We have developed many unique amplifiers, not only the universal BioAmp amplifier system. These facts ensure, that we can solve any special amplifier development task in biology and physiology. If you have any special request, please do not hesitate to contact us. We will provide a perfect solution quickly on a very reasonable price. The IonAmp amplifiers are good examples. Originally their prototypes were developed for a unique request. Then, during design procedures of several versions of IonAmp we decided to introduce them as standard products.
You can find the general warranty and shipping conditions in the beginning of the Price List page.
The prices of the different multi-channel BioAmp equipments are calculated according to the following algorithm. If the number of the channels in the system is increased according to the powers of 2, the price concerning one channel (the total price divided by the number of the channels) is always reduced by 16 %.
1-channel equipment: 1000 EUR (1000 EUR / channel)
2-channel equipment: 1680 EUR (840 EUR / channel)
4-channel equipment: 2820 EUR (705 EUR / channel)
8-channel equipment: 4736 EUR (592 EUR / channel)
16-channel equipment: 7952 EUR (497 EUR / channel)
Digital Offset Voltage Controller, built-in unit, 16-channel version: 270 EUR
Digital Offset Voltage Controller, built-in unit, 16-channel version: FREE if the number of channels is 4 or more.
Monopolar (single-ended) preamp for BioAmp in small metal box, without offset voltage correction circuit:
1-channel Monopolar preamp: 96 EUR (96 EUR / channel)
2-channel Monopolar preamp: 162 EUR (81 EUR / channel)
4-channel Monopolar preamp: 272 EUR (68 EUR / channel)
8-channel Monopolar preamp: 456 EUR (57 EUR / channel)
16-channel Monopolar preamp: 768 EUR (48 EUR / channel)
The first set of Monopolar (single-ended) headstage in the same channel number as the main amplifier, without offset voltage correction circuits: FREE if the number of channels is 4 or more.
Monopolar (single-ended) preamp for BioAmp, with built-in manual offset voltage correction circuit for every channel:
1-channel Monopolar preamp with offset correction: 192 EUR (192 EUR / channel)
2-channel Monopolar preamp with offset correction: 322 EUR (161 EUR / channel)
4-channel Monopolar preamp with offset correction: 540 EUR (135 EUR / channel)
8-channel Monopolar preamp with offset correction: 912 EUR (114 EUR / channel)
16-channel Monopolar preamp with offset correction: 1536 EUR (96 EUR / channel)
Differential (instrumentation) preamp for BioAmp in small metal box, without offset voltage correction circuit:
1-channel Differential preamp: 122 EUR (122 EUR / channel)
2-channel Differential preamp: 204 EUR (102 EUR / channel)
4-channel Differential preamp: 344 EUR (86 EUR / channel)
8-channel Differential preamp: 576 EUR (72 EUR / channel)
16-channel Differential preamp: 976 EUR (61 EUR / channel)
1-channel Preamplifiers (headstages) in cylindrical enclosure without offset voltage correction circuits. They are able to be moved by micromanipulators:
1-channel Monopolar (single-ended) headstage for BioAmp in small stainless steel enclosure: 190 EUR
1-channel Differential headstage for BioAmp in small stainless steel enclosure: 230 EUR
Intracellular preamplifier for single-channel BioAmp: 530 EUR
Optical isolator module for BioAmp, with built-in floating power supply, 0 to 20 kHz bandwidth, 2500 V rms isolation voltage: 210 EUR / channel
1 kVA mains isolation transformer with symmetrical secondary coil, in aluminum enclosure: 940 EUR
Unit Spike Detector (Action Potential Level Discriminator): 640 EUR
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