Global Specialties PB-503 - Manual - Manual (Page 10)

10
DESCRIPTION OF INDIVIDUAL FEATURES
In order to properly use the full capabilities of the PB-503, it is highly recommended that
the user become familiar with the panel layout and the features of the components.
(See Figure 1)
POWER SUPPLIES
By combining the three DC power supplies on the PB-503, the user may work with
virtually any type of integrated circuit or discrete component. The fixed 5 volt supply has
become an industry standard for powering digital IC's. IC's which require +5 V, +12 V,
and -5 V are easily accommodated by the PB-503. The variable supply output voltages
may be changed by using the screwdriver adjustment on the front panel. The positive
and negative outputs are continuously variable from +1.3 to +15 volts and -1.3 to -15
volts respectively. Both variable supply outputs are referenced to circuit common. This
creates a split supply which is often used with differential and operational amplifiers (op
amps). The adjustments are recessed to prevent inadvertent voltage changes which
could be destructive to a circuit.
FUNCTION GENERATOR
The multi-waveform function generator provides continuously variable frequency signals
from 0.1 Hz (for extra-low frequency work) to radio frequency signals of 100 KHz. The
frequency is selected in six decade ranges, with a slide potentiometer to adjust
frequency within each range. The sine wave output is factory adjusted for minimum
distortion. The triangle waveform is adjusted for best linearity. The standard square
wave and TTL level outputs are both set at a 5 0% duty cycle. The TTL output (available
when the function generator is set to Square Wave), capable of driving up to 10 TTL
loads, is continuously available and in phase with the square wave output. The low
output impedance of the sine, square, and triangle waveforms (600
Ω) assures
maximum coupling of the output signal to the device being driven. All outputs can
withstand a continuous short circuit to ground.
LOGIC INDICATORS
Sixteen LEDs, eight red and eight green, make up eight Logic Indicators that will display
logic high and low conditions based on either TTL or CMOS thresholds, selectable by
the user. Operating voltage can also be selected by the user to be either at +5 volts, or
at the setting of the 1.3 - 15 volts +V supply. This selection should be the same as the
operating circuitry that is to be monitored. The red LEDs will light when the voltages at
the inputs are 2.2 volts or higher when in the TTL position, or 70% of the operating
voltage or higher when in the CMOS position. The green LEDs will light when the
voltages at the inputs are 0.8 volts or less when in the TTL position, or 3 0% of the
operating voltage or less when in the CMOS position. An unconnected input, or an input
not at a valid logic level, will cause both LEDs to be extinguished. Note that the
thresholds determined by the TTL positions are only accurate when the +5 volt range is