ST AN2995 APPLICATION NOTE
AN2995
Demonstration board user guidelines
for single operational amplifiers
Introduction
This demonstration board is designed to help in the characterization of single operational
amplifiers in SOT23-5 (two different pinouts) and SC70-5 packages. Operational amplifiers
in SOT23-6 and SC70-6 packages can also be characterized, but their respective standby
pin cannot be used since it is connected to V
This document provides:
■ a brief description of the demonstration board.
■ a layout of the top and bottom layers.
■ some examples of typical configurations that can be tested with the board.
+ on the board.
CC
June 2009 Doc ID 15840 Rev 1 1/13
www.st.com
Board description AN2995
1 Board description
This board is designed with versatility in mind. In particular, its components allow it to be
configured as:
● a low-pass Sallen-Key circuit.
● a high-pass Sallen-Key circuit.
● a differential amplifier.
● an AC-coupled circuit.
● an in-loop compensation circuit.
● an out-of-loop compensation circuit.
● and numerous other possible configurations not described here.
The board is designed for surface-mounted components in SOT23-5 (and SOT23-6) or
SC70-5 (SC70-6) packages. It can be used to perform on-board characterization prior to the
integration of STMicroelectronics’ products in your designs. Resistor and capacitor
footprints are implemented in the 0805 series.
A set of two decoupling capacitors have been implemented on both power supply pins so as
to benefit from the maximum performances of ST products. In order to reject a wide range of
frequencies, 100 nF and 4.7 µF are good values for these capacitors.
Figure 1. Demonstration board schematics
Z14
Z4
VCC+
C1
C2
Vin2
Z8 Z3
Vin1
Z1
Z9
Z2
Z5
Vcc+
VCC-
Z6
SHDN
OP AMP
C3 C4
Z13
Vout
Z7 Z12
AM04501
2/13 Doc ID 15840 Rev 1
AN2995 Board layout
2 Board layout
The board has the following physical characteristics.
● Board dimensions: 2080 x 1900 mils (52.8 x 48.3 mm).
● 2-layer PCB.
For Vout, Vin1 and Vin2, male SMB or 2-mm female connectors can be implemented. You
can also implement test points on these three voltages to facilitate visualization of your
signals.
Figure 2 shows the top and bottom layers of the board.
Figure 2. Top and bottom layers
Doc ID 15840 Rev 1 3/13
Possible configurations AN2995
3 Possible configurations
This chapter provides instructions on how to set-up the board with several typical
configurations.
● Figure 3: low-pass Sallen-Key configuration
● Figure 4: high-pass Sallen-Key configuration
● Figure 5: differential amplifier configuration
● Figure 6: in-loop compensation configuration
● Figure 7: out-of-loop compensation configuration
● Figure 8: AC-coupled configuration
You can also connect several boards together if you need to evaluate more complicated
schematics using several operational amplifiers.
3.1 Low-pass Sallen-Key configuration
The low-pass Sallen-Key configuration is a second-order filter configuration. Z4 and Z9 are
used to set the gain.
Fc = 1/(2*PI*sqrt(Z1*Z2*C5*C6))
Z7, Z8, Z12 and Z14 must be "not connected". Z3 and Z13 must be shorted.
Figure 3. Low-pass Sallen-Key configuration
Z9
Vin1
Z2Z1
Z5
3.2 High-pass Sallen-Key configuration
Like the low-pass Sallen Key configuration, this is also a second-order filter configuration.
Z4 and Z9 are used to set the gain.
Fc = 1/(2*PI*sqrt(C1*C2*Z5*Z6))
Z7, Z8, Z12 and Z14 must be "not connected". Z3 and Z13 must be shorted.
Z4
Vout
Z6
AM04502
4/13 Doc ID 15840 Rev 1
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