Lecture notes
electronics notes
- Module
- Electronics
- Institution
- CIE
Detailed electronics notes with definitions, text, images, and additional info from 9702 past papers I have completed from , all variants
[Show more]
Seller
Follow
Content preview
ElectronicsOperational amplifier
A device which is integrated into circuits to produce an amplification or gain to the voltage
Components:
−¿ ¿
1. Inverting input (V )
−¿ ¿
2. Non-inverting input (V )
3. Positive voltage of power supply (+V s )
4. Negative voltage of power supply (-V s )
5. Output voltage (V out ¿
The two power supplies are of equal magnitude and the highest voltage an op-amp can
produce is the magnitude of the voltage of the power supply
2 Because net voltage = 1 in the inverting terminal
and if it was in the non-inverting terminal, the
output = -1 V
3 output voltage would be 1
If input = 5, and gain = 20, output = 5 x 20 = 100V
gain = 10
9
Net voltage = 1 in inverting terminal so input
4
output = -9V voltage = -1. Since gain = 10, output must be -1 x
10 = -10 but max input voltage = 9(or -9) so its
5
output voltage = -9V
-9
Characteristics of an ideal op-amp
1. Infinite input resistance
2. Infinite open loop voltage gain
3. Zero output resistance
4. Infinite bandwidth (an ideal op-amp will amplify signals of all frequencies)
5. Infinite slew rate (changes in output are instantaneous to changes in input – no time
delay between the two)
A comparator compares two voltage and the output depends on which voltage is greater.
The function of an op-amp is to use the potential differences between two inputs V+ and V−
to produce a large an output Vout as possible
Negative feedback
Connecting the output of an op-amp to the inverting input
Effects of negative feedback:
1. Reduced gain (if gain increases, distortion
increases)
2. Less distortion
3. Increased bandwidth
4. Increase stability of output voltage
, Inverting amplifier
Uses negative feedback
Non-inverting input is connected to the 0V line (earthed)
Input voltage and part of Vout is connected to the inverting input
Virtual earth approximation – an approximation in which the two inputs of an op-
amp are nearly at the same potential
Virtual earthing – when a point is made equal to zero volts by giving an equal and
opposite potential difference so both cancel out
Feedback resistor Rf
Why is point P earth?
The gain is infinite. Since V+ is earthed, for the amplifier to not saturate, point P
must be 0.
Point P is virtual earth if the amplifier is not saturated
Gain = output voltage/input voltage
If current in input resistor R(in) = I(in)
Current in feedback resistor (Rf) = I(f)
I(f) = -I(in)
V (¿) V (out)
Then =-
R(¿) R(f )
−R( f ) V (out)
And =
R(¿) V (¿)
V (out) −R ( f )
Since = gain, = gain
V (¿) R ( ¿)
Non-inverting amplifier
Input voltage is applied to the non-inverting input and part of the output voltage is
fed to the inverting input
As long as the op-amp is unsaturated, the p.d. between the inverting and non-
inverting input is almost zero and they are equal
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller advikasharma. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £3.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
56326 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now