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### Topic: DESIGN OF AN OP-AMP CIRCUIT. HELP!!! HELP!!! (Read 82 times)previous topic - next topic

#### Petir

##### Jun 13, 2016, 04:43 pm
I HAVE A PROJECT BUT NO IDEAS START FROM WHERE, BELOW IS THE QUESTION

Given that the pressure sensor produces an output voltage (Vs : sensor output voltage) according to the equation Vs = (P x 0.131 )+ 1.683. This equation can be expressed in terms of pressure (P) versus sensor voltage (Vs). ie.
P = (Vs - 1.683)/0.131

You are to design the amplifier circuit for this sensor using any combination of inverting amplifiers, non-inverting amplifiers, summing amplifiers together with a 1V reference voltage source. The two input signals of this circuit are sensor voltage (Vs ) and an 1V reference source (Vref ) and the circuit should produce an output voltage (Vo) indicating the pressure (psi) according to the equation Vo = P (psi)

i.e When P = 0 psi , Vo = 0V and
P = 10 psi, Vo = 10V.
P = -10 psi, Vo = -10V.

STANDARD VALUES FOR RESISTORS AND CAPACITORS
(a) The standard E-12 values for fixed resistors are in the following ratios: 1 : 1.2 : 1.5 : 1.8 : 2.0 : 2.2 : 2.7 : 3.3 : 3.9 : 4.7 : 5.6 : 6.8 : 8.2.
Examples: 100, 120, 150, 180, 220, 270, 330, 390, 470, 560, 680, 820Ω OR 1k, 1.2k, 1.5k, 1.8k, 2k, 2.2k, 2.7k, 3.3k, 3.9k, 4.7k, 5.6k, 6.8k, 8.2kΩ OR 10k, 12k, 15k, 18k, 22k, 27k, 33k, 39k, 47k, 56k, 68k, 82kΩ OR 100k, 120k, 150k, 180k, 220k, 270k, 330k, 390k, 470k, 560k, 680k, 820kΩ OR 1M, 1.2M, 1.5M, 1.8MΩ, etc.
(b) The ratios for the standard values of the various types of capacitors are as follows:
(i) pF range - 1: 1.2 : 1.5 : 1.8 : 2.2 : 2.7 : 3.3 : 3.9 : 4.7 : 5.6 : 6.8 : 8.2 Examples: 100pF, 120pF, 150pF, 180pF, 220pF, 270pF, 330pF, 390pF, 470pF, 560pF, 680pF, 820pF, etc. (
ii) nF range - 1: 1.2 : 1.5 : 1.8 : 2.2 : 2.7 : 3.3 : 3.9 : 4.7 : 5.6 : 6.8 : 8.2 Examples: 10nF, 15nF, 33nF, 47nF, 68nF, 82nF, 100nF, 150nF, 220nF, 330nF, 470nF, 680nF, etc.
(iii)µF range - 1: 1.2 : 1.5 : 1.8 : 2.2 : 2.7 : 3.3 : 3.9 : 4.7 : 5.6 : 6.8 : 8.2 Examples: 1µ, 2.2µ, 3.3µ, 4.7µ etc..

1. REWRITE THE EQUATION WITHE INPUT ON ONE SIDE AND OUTPUT ON OTHER SIDE
2. CHOSE THE AMPLIFIERS AND DESIGN
3. SCHEMATIC OR CIRCUIT DIAGRAMS
4. ERROR CALCULATION OF THE COMPONENT (MUST BE LESS THAN 5%)
5. COMPONENT LIST

#### gpsmikey

#1
##### Jun 13, 2016, 06:21 pm
You have actually been given much more useful information that most projects get to start with (like what the standard values are etc.).  You have also been given a reasonable set of steps to follow to get there - perhaps some study time with google etc. on op-amps etc. is in order instead of asking someone else to do your homework for you would be a good place to start.  The steps listed are in the correct order.
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3

#### knut_ny

#2
##### Jun 13, 2016, 06:25 pmLast Edit: Jun 13, 2016, 08:58 pm by knut_ny
Check if a voltage follower is neccecary for the sensor.

Build a non-inv. amp to make 1V -> 1.683V  (voltage from sensor for no pressure)
This shall cancel out the positive offset

Next amp:  sensor to positive input.
1.68V to negative input.

ampl. x 7.633

Use  simulator software to test you circuit.
-----------
alt II
1V -> -1.683    Then summing amp.
circuits
Ny

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