PubMed · 13867436
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
R BERANEK. 1962. [Amplifier input coil for microelectrodes].. https://pubmed.ncbi.nlm.nih.gov/13867436/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
We present the design and testing of a 16-channel analog amplifier for processing neural signals. Each channel has the following features: (1) variable gain (70-94 dB), (2) four high pass Bessel filter poles (f(-3 dB)=445 Hz), (3) five low pass Bessel filter poles (f(-3 dB)=6.6 kHz), and (4) differential amplification with a user selectable reference channel to reject common mode background biological noise. Processed signals are time division multiplexed and sampled by an on-board 12-bit analog to digital converter at up to 62.5k samples/s per channel. The board is powered by two low dropout voltage regulators which may be supplied by a single battery. The board measures 8.1 cm x 9.9 cm, weighs 50 g, and consumes up to 130 mW. Its low input-referred noise (1.0 microV(RMS)) makes it possible to process low amplitude neural signals; the board was successfully tested in vivo to process cortically derived extracellular action potentials in primates. Signals processed by this board were compared to those generated by a commercially available system and were found to be nearly identical. Background noise generated by mastication was substantially attenuated by the selectable reference circuit. The described circuit is light weight and low power and is used as a component of a wearable multichannel neural telemetry system.
PURPOSE: To improve preamplifier decoupling in a quadrature phased-array coil using a new quadrature combiner configuration. MATERIALS AND METHODS: A commercial six-element quadrature cervical-thoracic-lumbar (CTL) coil was used on a 1.5 T GE Signa Lx Scanner. The new combiner configuration is designed based on the fact that when one compares the amount of flux linkage of two loops with butterfly elements separated by the same distance, the loop elements have much higher coupling than the butterfly elements. RESULTS: The results are demonstrated using an imaging-based element coupling measurement method. The new quadrature combiner configuration has introduced an approximately -8dB improvement in preamplifier decoupling. CONCLUSION: One-dimensional quadrature phased arrays can be built even if the preamplifier is not integrated in the coil. If the combiner is placed between the coil and the preamplifiers, the butterflies should be on the high impedance side of the quadrature combiner. The loops should see the low input impedance of the preamplifiers.
This paper describes the circuitry and construction of a novel electronic threshold discriminator, and details its specific application to in vivo intracellular recording. The discriminator reliably triggers electrophysiological recording at pre-selectable membrane potentials in neuronal systems that exhibit membrane potential oscillations. It has been used successfully whilst recording from spiny projection neurons of the striatum to measure membrane properties and trigger electrical stimulation within either of two discrete membrane potential "states". The device works by comparing the analogue membrane potential waveform with a user-defined threshold membrane potential, and outputs a logic signal to flag the occurrence of a threshold-crossing event. This signal is used to trigger the commencement of episodic recording and the application of current injection or electrical stimulation at a consistent membrane potential. Thus, the discriminator acts as a functional clamp to isolate evoked responses from endogenous fluctuations in membrane potential. The unit uses cheap and easily available components and can be constructed with the minimum of electronics experience. It could be adapted to isolate discrete events within any oscillatory system.