Isolation amplifiers provide electrical isolation and safety barriers between input and output stages. They use transformer, optical, or capacitive isolation methods and isolated power supplies to break continuity while amplifying low-level signals. Common applications include medical equipment, industrial processes, and data acquisition where electrical isolation is needed to protect patients or eliminate noise.

2.  Isolation
amplifiers provide electrical isolation
and an electrical safety barrier.
 They protect the patients from leakage
currents.
 They break the ohmic continuity of electrical
signals between input and output.
 Isolated power supplies are provided for both
the input and output stages.
 Used to amplify low level signals.

4. Three types of methods are used to design isolation
amplifier



Transformer isolation
Optical isolation
Capacitive isolation

6. It uses either frequency modulated or a pulse
width modulated carrier signal.
 Internally it has 20KHz oscillator, transformer,
rectifier and filter to provide supplies for each
isolated stages.
 Rectifier- input to primary OPAMP.
 Transformer- couples the supply.
 Oscillator – input to secondary OPAMP.
 A low pass filter is used to remove the other
frequency components.


7. 


High common mode rejection ratio
High linearity
High accuracy

9.  MEDICAL
Patient Monitoring and Diagnostic
Instrumentation
 INDUSTRIAL
Ground Loop Elimination and
Off-ground Signal Measurement
 NUCLEAR
Input/output/Power Isolation

11.  The
biological signal is converted into a light
signal by LED for further process.
 It has patient circuit which is the input circuit
and a phototransistor which forms the output
circuit.
 Each circuit is battery driven.
 The input circuit converts the signal to light
and the output circuit converts the light back to
signal.

13. Original frequency and amplitude is obtained.
 High linearity.
 No modulator or demodulator is needed as it
couples optically.
 Improves patient safety


14.  INDUSTRIAL PROCESS
CONTROL
 DATA ACQUISITION
 INTERFACE
ELEMENT
 BIOMEDICAL MEASUREMENTS
 PATIENT MONITORING
 TEST EQUIPMENT
 CURRENT SHUNT MEASUREMENT
 GROUND-LOOP ELIMINATION
 SCR CONTROLS

16. It uses digital encoding of the input voltage and
frequency modulation.
 The input voltage is converted to proportional
charge on the switched capacitor.
 It has modulator and demodulator circuits.
 The signals are sent across a differential capacitive
barrier.
 Separate supplies are given for both sides.


18. Ripple noises are removed.
 It avoids device noise, radiated noise and
conducted noise.
 High immunity to magnetic noises.
 Useful for analog systems.
 Has high gain stability and linearity.


19. 




DATA ACQUISITION
INTERFACE ELEMENT
PATIENT MONITORING
ECG
EEG

20. 


Commonly used
Transformer isolation amplifier
Cost
Optical- low cost due to less components
Transformer
Capacitor coupled- high cost
Isolation voltage
Optical- low (800V)
Transformer- medium (1200V)
Capacitance- high (2200V)

21. 

Isolation resistance
Optical- 10^12
Transformer- 10^10
Capacitance- 10^12
Gain stability and Linearity
Optical- 0.02%
Transformer- between 0.005% and 0.02%
Capacitance- 0.005% (best)