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

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

Circuits Circuits Everywhere!




In the last section, we saw how a very simple transmitter worked. It was made up of several different types of electronic components, including capacitors, transistors, resistors, etc. When we assemble several types of electronic components in a configuration that serves some purpose, we call it a CIRCUIT.

Some common electronic components are:
Wire
Resistors
Capacitors
Coils
Transformers
Tubes
Transistors
Diodes


All circuits are combinations of individual electronic components assembled to perform a function. The "type" of circuit it is, depends on the function of the circuit. We have already discussed some simple circuits, called "filters", and have also gone through "power supplies". Now we have introduced you to "amplifiers".

Here is a list of some of the major types of circuits we will discuss and explain how they operate:
Power Supplies
Filters
Amplifiers
Oscillators
Mixers
Logic Circuits
Almost any device or type of electrical equipment is made up of a COMBINATION of these circuits.

Basic Circuits combine to make Complex Circuits
Our transmitter, for instance, is an Audio Amplifier, which drives an RF Mixer, which has a second input from the RF Oscillator (High Frequency Generator). The Mixer combines the inputs from the Audio Amp and the Oscillator to create a radio signal that is modulated by the audio signal, which then goes out to the antenna.

Of course this is an over simplification of what really has to happen, but the point is, that it is ALL done by basic circuits, and that if you learn and understand the simple circuits, you can look at VERY complex devices, and understand how they work!

We need to discuss each of the basic types of circuits in greater detail until you fully comprehend the theory behind how they work. Then you will have a firm grasp on electronics, and can begin combining them to create useful circuits.

First, let's cover the two electronic components we haven't covered yet:
Transistors and Diodes.