RHS Stim/Amplifier Chips
The RHS2116 stim/amplifier chip is a complete bidirectional electrophysiology interface with 16 independent stimulator/amplifier channels. Each channel integrates a configurable low-noise biopotential amplifier and a programmable constant-current stimulator capable of generating stimulation pulses for extracellular microelectrodes.
Electrode signals can be connected directly to the chip and a digital bus is used to control stimulation and read digitized electrode signals. By interfacing electrodes directly with a standard digital SPI bus, the RHS2116 replaces all analog instrumentation circuitry in extracellular recording and stimulation systems.
The RHS2116 is suitable for a wide variety of neural interfacing applications. Innovative circuit architecture combines stimulators, charge recovery circuits, amplifiers, filters, a 16-bit ADC, and impedance measurement on a single silicon chip.
Programmable registers configure the upper and lower bandwidths of the amplifiers. This flexibility allows the chips to be optimized for different types of electrophysiological signals including EKG, EMG, ECoG, EEG, neural spikes, and local field potentials. Integrated charge-recovery circuits and fast amplifier settling can be employed following stimulation pulses to minimize recording artifacts. Here are actual biological signals acquired using RHS2116 chips.
Our RHS stim/recording system includes headstages using RHS2116 chips. This system offers a quick way to evaluate the performance of these chips with a plug-and-play USB interface and open-source, multi-platform GUI software. Intan Technologies also provides an open-source API to control multiple RHS2000 chips from a host computer.
RHS2000 Family
- RHS2116 16-channel stimulator/amplifier chip with unipolar inputs and common reference
Features
- Fully integrated electrophysiology interface chip with amplifiers, stimulators, and industry-standard serial peripheral interface (SPI)
- Stimulators source and sink currents ranging from 10 nA to 2.55 mA over an 14V range with integrated compliance monitors
- Integrated charge-recovery circuits and fault current detection module
- 16-bit ADC samples amplifiers up to 40 kSamples/s per channel
- Low noise floor: 2.4 μV rms typical
- Upper cutoff frequency configurable from 100 Hz to 20 kHz
- Lower cutoff frequency configurable from 0.1 Hz to 1000 Hz
- Fast amplifier artifact recovery for post-stimulus recording
- Integrated multi-frequency in situ electrode impedance measurement capability
Applications
- Miniaturized multi-channel headstages for neural recording and stimulation
- Low-power wireless headstages or backpacks for electrophysiology experiments
- Microelectrode array (MEA) in vitro recording and stimulation systems
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| RHS2116 16-channel stimulator/amplifier chip in QFN package and in bare die form. |
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Important Change to RHS2116 Specifications
In May 2021, we identified a hardware degradation mode in the RHS2116 chip. When powering these chips from a ±9V supply, the anodic (positive) current generator in each stimulator circuit begins to fail after many stimulation pulses, typically in the range of 30,000 to 1 million pulses. After degradation, the positive current output will be too low, often zero. This is a permanent hardware failure that cannot be reset by power-cycling the chip.
The cathodic (negative) current generators do not degrade.
We have run extensive tests and determined that lowering the supply voltage to ±7V protects the chip against these failures. We have tested RHS2116 chips to more than 100 million stimulation pulses at these supply levels with no anodic current failures observed.
All customers using RHS2116 chips are advised to reduce power supplies to no more than ±7V (or a total difference between VSTIM+ and VSTIM- of 14V) to avoid long-term degradation of anodic current generators on the chip.
