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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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Build a Simple Quiz Master Circuit Diagram

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How to Build a  Simple Quiz Master Circuit Diagram, Quiz master is a device which uses electronics to decide who pushes their button first, Up to eight players each have their own answer button to press, corresponding to the four Red Team and four Green Team LEDs on the master control board. As soon as the first contestant who thinks that he knows the answer presses the button, a loud tone sounds, all other contestants are locked out, and the contestant`s indicator LED lights on the control board so that it`s obvious who buzzed in first. 

The control board also features two selectable time out periods each adjustable from 3 to 15 seconds, setting specified time intervals in which the player must answer before the time`s up! tone sounds. Eight SCRs form the heart of the circuit. The anode of each SCR has a positive (+) bias on it by way of an LED and a negative (-) bias on cach cathode. As soon as a contestant depresses his or her switch button (S4 through Sll), a positive bias is applied to the respective SCR gate. 

Simple Quiz Master Circuit Diagram





That bias latches the contestant`s SCR on, which in turn lights up the appropriate LED on the master control board. At the same time, the activity of the SCR latching on turns on the answer buzzer (BZ) and locks out all other contestants. The lockout occurs because relay K2 contacts operate to remove the availability of a bias voltage to the gate of the other SCRs. The other circuitry consists of a timer circuit and a time`s-up tone-generating circuit. 

The timer circuit consists of transistor Ql, capacitor CI, resistors Rl through R3, and trimmer resistors PI and P2, Depending on the adjustment of the trimmer resistors and selection switch S3, a specific time period can be set. The lime`s-up tone-generating circuit is made up of IC1, transistors Q2 and Q3, and the associated resistors and capacitors. The on time of the tone can be set by P3. Relay Kl, which is operated by the timer circuit, serves to reset the entire unit for the next question.

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