Unformatted text preview: SMALL for Big Things University at Buffalo SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York nanobioSensors & MicroActuators Learning Lab The State University of New York EE 203 Circuit Analysis 2
Lecture 33
Chapter 5.1
Operational Amplifier
Terminals
Kwang W. Oh, Ph.D., Assistant Professor
SMALL (nanobioSensors and MicroActuators Learning Lab)
Department of Electrical Engineering
University at Buffalo, The State University of New York
215E Bonner Hall, SUNYBuffalo, Buffalo, NY 142601920
Tel: (716) 6453115 Ext. 1149, Fax: (716) 6453656
Email: [email protected], http://www.SMALL.Buffalo.edu EE 203 Circuit Analysis 2  Spring 2008  Prof. Kwang W. Oh  [email protected] OP Amp (Operational Amplifier)
OP Amp is referred to as operational
because it was used to implement the
mathematical operations of
Integration, Differentiation, Addition, Sign
Differentiation Addition Sign
changing, Scaling, and more applications.
The terminals of primary interest
3. Noninverting input
2. Inverting input
6. Output
7. Positive power supply (V+ )
4. Negative power supplly (V – )
8. NC (no connection)
1. & 5. Offset null no concern Lecture 33  Chapter 5  1/4  1/9 EE 203 Circuit Analysis 2  Spring 2008  Prof. Kwang W. Oh  [email protected] SMALL for Big Things University at Buffalo SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York nanobioSensors & MicroActuators Learning Lab The State University of New York Lecture 33  Chapter 5  1/4  2/9 OP Amp
EE 203 Circuit Analysis 2
Lecture 33
Chapter 5.2
Terminal Voltages, Currents Terminals
Terminals
3. (+) Noninverting input
2. ( –) Inverting input
6. Output
7. (V+) Positive power supply (V+)
4. (V –) Negative power supply (V –) EE 203 Circuit Analysis 2  Spring 2008  Prof. Kwang W. Oh  [email protected] Kwang W. Oh, Ph.D., Assistant Professor
SMALL (nanobioSensors and MicroActuators Learning Lab)
Department of Electrical Engineering
University at Buffalo, The State University of New York
215E Bonner Hall, SUNYBuffalo, Buffalo, NY 142601920
Tel: (716) 6453115 Ext. 1149, Fax: (716) 6453656
Email: [email protected], http://www.SMALL.Buffalo.edu Lecture 33  Chapter 5  1/4  3/9 EE 203 Circuit Analysis 2  Spring 2008  Prof. Kwang W. Oh  [email protected] Lecture 33  Chapter 5  1/4  4/9 SMALL for Big Things University at Buffalo SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York nanobioSensors & MicroActuators Learning Lab The State University of New York Terminal Voltages and Currents Voltage Transfer Characteristic of an OP Amp A positive supply voltage (VCC) is connected between V+ and the common node.
positive
A negative supply voltage ( –VCC) is connected between V – and the common
node.
vp, vn, vo
All the current reference directions are into the terminals of the OP amp
in, ip, io, ic+, ic– EE 203 Circuit Analysis 2  Spring 2008  Prof. Kwang W. Oh  [email protected] The
The output voltage is a function of the difference between the input
voltages (vp – vn).
The output voltage = the difference (vp – vn) in its input voltages times the
ou
multiplying constant, or gain A
Linear region: the output voltage is a linear function of the input voltages,
when
when vp – vn is small
Positive saturation & negative saturation: the output voltage is no longer a linear
function of the input voltages. Lecture 33  Chapter 5  1/4  5/9 EE 203 Circuit Analysis 2  Spring 2008  Prof. Kwang W. Oh  [email protected] SMALL for Big Things University at Buffalo SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York nanobioSensors & MicroActuators Learning Lab The State University of New York Constraint Input Voltage Constraint for Ideal OP Amp A constraint is imposed on the input voltages, vp and vn
and
The constraint is based on typical numerical values for VCC and A.
Typical OP Amp
Recommended dc power supply voltages seldom exceed 20 V
The gain, A, is rarely less than 104.
–VCC ≤ A(vp – vn) ≤ VCC
–20 ≤ 104(vp – vn) ≤ 20
vp – vn ≤ 20/104 = 2 mV
Note that the positive and negative power supply voltages do not have to be
equal in magnitude.
For example, iif V+ = 15 V and V – = –10 V, then –10 V ≤ v0 ≤ 15 V
f
15
10
15
Be aware also that the value of A is not constant under all operating conditions.
For now, however, we assume that it is.
EE 203 Circuit Analysis 2  Spring 2008  Prof. Kwang W. Oh  [email protected] Lecture 33  Chapter 5  1/4  6/9 Lecture 33  Chapter 5  1/4  7/9 Input voltage constraint for ideal OP Amp
Infinite A
vp – vn ≤ 20/104 = 2 mV
vp – vn ≤ 20/∞ = 0 Virtual short condition
Negative feedback: a signal is fed back from the output terminal to the inverting
input terminal
Negative feedback the input voltages difference (↓) the output voltage (↓)
OP Amp operates in its linear region. EE 203 Circuit Analysis 2  Spring 2008  Prof. Kwang W. Oh  [email protected] Lecture 33  Chapter 5  1/4  8/9 SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York Input Current Constraint for Ideal OP Amp
Input current constraint for ideal OP Amp
Infinite equivalent input resistance
The equivalent resistance seen by the input terminals of the op amp is very large,
typically 1 MΩ or more. Even though the current at the input terminal is negligible, there
may still be appreciable current at the output terminal EE 203 Circuit Analysis 2  Spring 2008  Prof. Kwang W. Oh  [email protected] Lecture 33  Chapter 5  1/4  9/9 ...
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This note was uploaded on 10/19/2011 for the course EE 203 taught by Professor Staff during the Spring '08 term at SUNY Buffalo.
 Spring '08
 Staff
 Amplifier, Operational Amplifier

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