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SECTTON
Principles
of
Operation
2.2.6
Power Supply Section
The power supply provides several DC operating volt-
ages to various other sections in the instrument. Supply
voltages include 24V, 15V, and +5V DC.
Note that power supply common is connected to chassis
ground.
2.3
ANALOG CIRCUIT DESCRIPTION
2.3.1
Analog Section Block Dlagram
Figure 2-2 shows a block diagram of the analog section of
the in&rument. Key sections include the D/A converter,
square wave generator, amplitude modulation circuits,
and multiplying
D/A and attenuator for amplitude and
DC offset control.
2.3.2
D/A Converter
Digital waveform data from the synthesizer is converted
into an analog signal by the D/A converter. The con-
verted signal is then passed through a low-pass filter to
remove any spurious components. This conversion proc-
ess is used to generate sine, triangular, and sawtooth
waves.
2.3.3
Square Wave Generator
Square waves with fixed 50% duty cycle are generated by
applying sine waves to an analog comparator. The ana-
log comparator has a certain amount of hysteresis, which
results in good-quality square waves at the output.
Variable duty cycle square waves are generated by a digi-
tal comparator. Digital sawtooth waveform information
is used as the input signal to the digital comparator.
2.3.4
Amplltude Modulation
A signal applied to the AM IN jack can be used to ampli-
tude modulate the output signal. This modulating signal
is applied to the AM multiplier,
which performs the
modulating function.
2.3.5
Amplitude and DC Offset Control
Control of the AC amplitude and DC offset amplitude is
performed the multiplying
D/A section in conjunction
with the output amplifier. Further amplitude control is
provided by the output attenuator, which includes 1:lO
and 1:lOO attenuation ratios. Combining these two ratios
yields overall attenuation ratios of l:l, l:lO, l:lOO, and
1:lOOO.
2-3
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