System Architecture And Theory Of Operation - Intan Technologies CLAMP User Manual

Intan CLAMP System

System Architecture and Theory of Operation

Traditional Analog Patch Clamp Amplifier
The diagram above shows the major functional components of a traditional patch clamp amplifier system. A traditional analog
headstage module contains sensitive analog electronics that act as a pre-amplifier with voltage clamp and current clamp capability.
In voltage clamp mode, the headstage measures the electrode current and converts this to a proportional small voltage. In current
clamp mode, the headstage buffers the electrode voltage but provides no additional amplification. Voltage and current clamp
control is provided by analog voltages that convey the desired clamping levels.
The headstage is connected to a remote computer-controlled amplifier via a shielded interface cable that carries small analog
voltages (typically in the millivolt range) and is thus susceptible to noise pickup. The amplifier module / digitizer consists of one or
more rack-mounted boxes that contain additional analog amplifiers, analog-to-digital converters (ADCs), digital-to-analog
converters (DACs), and a digital controller that coordinates control of these devices. The amplifier module and digitizer are
interfaced to a host PC that sequences particular experiments and records the measured data.
Intan Digital Patch Clamp Amplifier
The CLAMP chips from Intan Technologies combine all analog circuitry and many digital control blocks on a single chip, permitting
the construction of Intan-powered digital headstages (see diagram above). A small circuit board containing an Intan CLAMP
chip and a small number of support components form a complete patch clamp amplifier with a purely digital interface. The Intan
digital "headstage" is actually a complete, miniaturized patch clamp amplifier. Thanks to the integration of nearly all patch
clamp circuit elements onto a single silicon chip (see "actual size" inset above), the Intan-powered patch clamp amplifier is smaller
than many traditional analog headstages that perform only a small fraction of the total amplification task.
The digital interface cable uses a standard serial communication protocol (Serial Peripheral Interface, or SPI) and is no longer
susceptible to noise pickup. Sensitive analog signals are digitized at the source, not several meters away. The purely digital
interface makes it easy to electrically isolate each headstage and eliminate ground loops. The need for a large computer-controlled
amplifier module is completely eliminated, replaced by an Intan CLAMP controller that can easily control multiple digital
headstages simultaneously.
To preserve legacy "external command" and "signal monitor" functions associated with traditional patch clamp systems, the Intan
CLAMP controller incorporates ADCs and DACs to allow for real-time control of voltage and current clamp via analog voltages (in
addition to software clamp control), and real-time monitoring of measured and/or clamp voltages/currents via analog signals.
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