TAN-005 Datasheet, PDF (1/8 Pages) Exar Corporation – High-Quality Function Generator System with the XR-2206

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TAN-005
High-Quality Function Generator
System with the XR-2206
INTRODUCTION
Waveform or function generators capable of producing
AM/FM modulated sine wave outputs find a wide range of
applications in electrical measurement and laboratory
instrumentation. This application note describes the
design, construction and performance of such a complete
function generator system suitable for laboratory usage
or hobbyist applications. The entire function generator is
comprised of a single XR-2206 monolithic IC and a limited
number of passive circuit components. It provides the
engineer, student, or hobbyist with a highly versatile
laboratory instrument for waveform generation, at a very
small fraction of the cost of conventional function
generators available today.
GENERAL DESCRIPTION
The basic circuit configuration and the external
components necessary for the high-quality function
generator system is shown in Figure 1. The circuit shown
is designed to operate with either a 12V single power
supply, or with 16V split supplies. For most applications,
split-supply operation is preferred since it results in an
output dc level which is nearly at ground potential.
The circuit configuration of Figure 1 provides three basic
waveforms: sine, triangle and square wave. There are
four overlapping frequency ranges which give an overall
frequency range of 1Hz to 100KHz. In each range, the
frequency may be varied over a 100:1 tuning range.
The sine or triangle output can be varied from 0 to over 6V
(peak to peak) from a 600W source at the output terminal.
A squarewave output is available at the sync output terminal
for oscilloscope synchronizing or driving logic circuits.
TYPICAL PERFORMANCE CHARACTERISTICS
The performance characteristics listed are not
guaranteed or warranted by EXAR Corporation.
June 1997-3
However, they represent the typical performance
characteristics measured by EXAR’s application
engineers during the laboratory evaluation of the function
generator system shown in Figure 1. The typical
performance specifications listed below apply only when
all of the recommended assembly instructions and
adjustment procedures are followed:
(a) Frequency Ranges: The function generator system
is designed to operate over four overlapping
frequency ranges:
1Hz
to
10Hz
to
100Hz to
1KHz
to
100Hz
1KHz
10KHz
100KHz
The range selection is made by switching in different
timing capacitors.
(b) Frequency Setting: At any range setting, frequency
can be varied over a 100:1 tuning range with a
potentiometer (see R13 of Figure 1.)
(c) Frequency Accuracy: Frequency accuracy of the
XR-2206 is set by the timing resistor R and the timing
capacitor C, and is given as:
f = 1/RC
The above expression is accurate to within 15% at any
range setting. The timing resistor R is the series
combination of resistors R4 and R13 of Figure 1. The
timing capacitor C is any one of the capacitors C3
through C6, shown in the figure.
(d) Sine and Triangle Output: The sine and triangle
output amplitudes are variable from 0V to 6Vpp. The
amplitude is set by an external potentiometer, R12 of
Figure 1. At any given amplitude setting, the triangle
output amplitude is approximately twice as high as the
sinewave output. The internal impedance of the output
is 600W.
Rev. 1.02
E1995
EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 z [phone] z FAX [phone]
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