1. T.C. DOĞUŞ UNIVERSITY
CEE 426
Microelectronic Analog Circuit Design
Opamp Analysis
AD8538ARZ
By
Tolgahan ŞUSUR
200934005

2. AD8538ARZ
INTRODUCTION
Analog Devices Inc. announced a series of low-cost
amplifiers that operate at low voltages and consume
minimal power without sacrificing the accuracy
required by portable applications that need precise
signal conditioning. To extend battery life, amplifiers
must offer very low operating and standby power,
low-voltage operation, and rail-to-rail outputs.
Auto-zero Amplifier
The AD8538 offers the industry’s best accuracy
versus power among auto-zero amps on the market, and is ideal for signal paths with very low
offset voltage and offset voltage drift over time and temperature.
More about the AD8538
Requiring a supply current of only 150 microamps, the AD8538 offers three times better
temperature drift performance compared to the closest competing device a drift performance
level equivalent to products requiring over 1 mA of supply current. Its low power and high
precision makes the AD8538 well-suited for markets such as medical equipment, pressure and
thermal sensors and automotive electronics.
With only 0.01 microvolt/degree C offset drift, the AD8538 offers the industry’s lowest offset
drift at low operating current. The device offers tremendous cost and time savings to
designers as compared to a discrete system-level auto-calibration approach, which requires
more complicated and costly hardware and software that can slow down time-to-market for
new products. The device’s outstanding precision – 12 microvolts maximum offset and just 1
microvolt p-p of low-frequency noise — enable highly accurate and stable system designs
without the cost, size and complexity of solutions utilizing external auto-calibration.
Applications
For the AD8538, typical high-resolution portable sensor applications, such as IR thermal
scanners, require very low offset and offset drift to achieve accurate measurements.
Pricing and Availability
The AD8538, available now in production quantities, is packaged in both TSOT-23 and
narrow SOIC-8 packages and is priced at $0.89 per unit in 1,000-piece quantities.

3. Brief properties
The AD8538 is a very high precision auto-zero amplifier that features extremely low offset
voltage and low input bias current while consuming low power. The supply current is less
than 180 µA at 5.0 V. Operation is fully specified from 2.7 V to 5.0 V single supply (±1.35 V
to ±2.5 V dual supply). The AD8538 offers tremendous cost and time savings to designers as
compared to a discrete system-level autocalibration approach, which requires complicated and
costly hardware and software that can slow down time-to-market for new products. The
AD8538 amplifier is available in 5-lead TSOT-23 and 8-lead SOIC and is specified over the
extended industrial (–40°C to +125°C) temperature range. The application circuit's closedloop gain is set for 101
Using for ;
Mobile Communication
Portable Instrumentation
Battery Powered Devices
Sensor Interface
Temperature measurement
Electronic Scales
Figure.1: AD8538 Thermometer circuit

4. MEASUREMENTS AND SIMULATIONS
In my measurements , I use PSPICE and PROTEUS softwares. But ı rarely use PROTEUS because ıt is
easy to get measurement also there is more component library than PSPICE . In addition there is
more graphical properties and very user friendly menus for simulations. For simulation I apply
buffer and non inverting circiut with AD8538ARZ. In simulations I use Pulse,DC and Sin waves
Figure.2: All circuit and Pulse generator properties for Buffer circuit
Figure.3: Pulse Generator amplitude and Frequency (+-15 volt)

5. RATED VOLTAGES OF AD8538ARZ
Figure.4:Vout , output voltage (Supply voltages are +-15v)
As we can see above in figure 4 there is a rated voltage which is +-14 volt .
SLEW RATE OF AD8538ARZ
Figure.5:Slew rate is 0.45v/us (Supply voltages are +-3v)

6. FREQUENCY ANALYSIS OF AD8538ARZ
Figure.6:Frequency responce analysis, fb=632kHz ft=50MHz A0=45dB=177.8
There is a some problems about gain because ft=fb*A0=50Mhz =632kHz*A0
A0=79 But my graph value 177.8 so there is conflict or my measurement is false.
INPUT CURRENT AND EMPEDANCE OF AD8538ARZ
R1=1K
R2=1K
Figure.7: Input voltage and input empedance, input current (Input=4v DC )
We can see that our input voltage=4 volt input current=18pA so input empedance
4/18pA=222G ohm. So there is a high empedance at input like infinite

7. OFFSET VOLTAGES OF AD8538ARZ
Figure.8 Offset voltages
There is gain 1/1+1=2 and our vout value is 115uV/2=57.5uV offset voltage
R1=1K
R2=1K Vsupply=+-15v
SETTLING TIME OF AD8538ARZ

8. Figure.9: Settling time (input +10m-0v pulse wave supply :+-15v dc)
We can calculate the settling time with these steps;
10.5mv (hill point of vout )-10mv/10mv =0.05
100*0.005=%0.5 settling time
SUPPLY CURRENT OF AD8538ARZ
Figure.10:Supply current (Buffer circuit)
As we can see above ı measure the current with dc ammeter and ı see that values
Input current =0.33mA=330uA
REFERENCE
1. http://www.radiolocman.com/news/new.html?di=4499
2. http://www.analog.com/static/imported-files/data_sheets/AD8538_8539.pdf