# I need help bad can someone help

#### dmanzay

Joined Oct 25, 2011
5
I need to design a circuit, using Op-amps to display the solution of the following equation: x + 2y = z. I have never done this and don't know what to start. Can some one help. I need to build a circuit to match the block diagram.

Andre

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#### Wendy

Joined Mar 24, 2008
22,343
You are trying to build a analog computer. I can give you a couple of hints.

Voltages equal numbers. If x=-1 then the input you designate as X is -1 volts. It can actually be any voltage, since the reading device can be calibrated however you want, but since you will likely be using a DVM this would be a good start.

Multiplication and division is gain. The input for Y would have to have a gain of 2.

Look for the chapter on summing op amps.

#### SgtWookie

Joined Jul 17, 2007
22,221
Your subject line should say something about what you wish to do, not just that you need help badly.
For example, "Opamp circuit to solve equation help" would be much more meaningful and helpful to people who might wish to help you.

Start here:

You have two inputs: x and y.
I suggest that for the input x, you need a voltage follower/buffer. The way to wire one of these is shown at the top of the "negative feedback" page.

Then you need to multiply y by two. So, you need a non-inverting amplifier with a gain of 2. If you keep reading the "negative feedback" section, you will find out how to do this.

Then you need to find out how to add the results together. You can find out how to do that in the "averager and summer circuits" section:

The way to solve this problem is like eating an elephant - one bite at a time.
[eta]
Bill beat me to it...

#### dmanzay

Joined Oct 25, 2011
5
Hello Bill can you point me to where a circuit built this way will be. Me looking at circuit close to what I need to build will help me more give me a better clue.

#### dmanzay

Joined Oct 25, 2011
5
Thanks SgtWookie
I understand what you meant by the subject line.

#### Wendy

Joined Mar 24, 2008
22,343