# A circuit having 2 inputs and 2 outputs

Discussion in 'General Electronics Discussion' started by adrian11, Jan 7, 2015.

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Jan 7, 2015
I am going to design a circuit that should have 2 inputs and 2 outputs.

when both inputs are low both outputs should be low

when input 1 is high and input 2 is low, output 1 should be a square wave alternating between 0(low) and 1(high) with duty cycle 50%. output 2 should be low

when input 2 is high and input 1 is low, output 2 should be high. output 1 should be low

when both inputs are high both outputs should be low.

I need some of your ideas on how this is to be done.

2. ### Laplace

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Apr 4, 2010
The standard way to do this is to create a truth table. Then from the truth table create a Karnaugh map for each output. Since Output#1 is always LOW except when it is a square wave, set Output#1 to be HIGH for the square wave condition and use Output#1 with an AND gate and square wave generator to create a gated square wave. Minimize the K-maps to get the structure of the logic gates necessary to satisfy the truth table.

3. ### KrisBlueNZSadly passed away in 2015

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Nov 28, 2011
Have a look at the CD4052B (CMOS 4000 series) and the 74HC153 (74xx HCMOS series). These are both dual multiplexers with two sets of four inputs and two outputs, and two control inputs to select which inputs are directed to the outputs.

You will also need an oscillator. There are lots of ways to make these; a simple one is a Schmitt trigger inverter with a capacitor from the input to 0V and a resistor (or trimpot or potentiometer) from the output to the input. You can use a CD4093 (quad 2-input NAND gate with Schmitt trigger inputs), CD40106 (hex inverter with Schmitt trigger inputs), or a single-gate inverter with Schmitt trigger inputs such as the BU4S584G2.

If you need exactly 50% duty cycle you can operate the oscillator at twice the desired frequency and feed it through a divide-by-two stage such as half a CD4013 or 74HC74 connected with Q-bar to D so it will act as a toggle flip-flop, or a cascaded divider such as the CD4024 or CD4040.