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High CMRR Instrumentation Amplifier (Schematic and Layout) design for biomedical applications

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Instrumentation amplifiers are intended to be used whenever acquisition of a useful signal is difficult. IA’s must have extremely high input impedances because source impedances may be high and/or unbalanced. bias and offset currents are low and relatively stable so that the source impedance need not be constant. Balanced differential inputs are provided so that the signal source may be referenced to any reasonable level independent of the IA output load reference. Common mode rejection, a measure of input balance, is very high so that noise pickup and ground drops, characteristic of remote sensor applications, are minimized.Care is taken to provide high, well characterized stability of critical parameters under varying conditions, such as changing temperatures and supply voltages. Finally, all components that are critical to the performance of the IA are internal to the device. The precision of an IA is provided at the expense of flexibility. By committing to the one specific task of
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Simple Thermocouple Preamplifier Circuit Diagram

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This is a Simple Thermocouple Preamplifier Circuit Diagram. Thermocouple, a local temp sensor and a summing amplifier you can design a practical preamplifier. As a project goal, let's design a circuit. The MAX420 is operated at a gain of 191 to convert the 52 p.VI o C output of the type J thermocouple to a 10 mV/°C signal. The -2.2 mV/°C tempco of the 2N3904 is added into the summing junction with a gain of 42.2 to provide cold-junction compensation. 


Simple Thermocouple Preamplifier Circuit Diagram
 
 The ICL8069 is used to remove the offset caused by the 600-m V initial voltage of the 2N3904. Adjust the 10-KO trimpot for the proper reading with the 2N3904 and isothermal connection block at a temperature near the center of the circuit` s operating range. Use the component values shown in parentheses when using a type K thermocouple.

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