Section Il. STAGE FUNCTIONING

11-6660-204-25

Section Il. STAGE FUNCTIONING

a. The cathode follower circuit receives its

2-3. Cathode Follower

i n p u t signal through. SIGNAL SELECTOR

(figs. 2-1 and 2-2)

switch S202, which is mounted on the control

Cathode follower V301A is one-half of a minia-

panel. This switch has four positions and its rotor

ture twin-triode tube which functions as a buffer

contact is connected to) the input (grid) of the

or isolating stage and offers a sufficiently high

c a t h o d e follower. One position, S.C. (short

input impedance to prevent loading of the output

circuit ), is used to ground the input, and effects a

circuit of the radiosonde receiver (which supplied

zero indication on the recorder. Two test-voltage

signals to the recorder). The cathode follower

positions, 60 CPS and 120 CPS, supply either a

presents a low output impedance to the noise-sup-

60- or 120-CPS signal to the input circuit, which

pression circuit and the input signals can be in

makes the recorder indicate a reference level of 30

the form of sine waves, exponential waves, saw-

or 60 chart divisions, respectively, when REF.

tooth waves, or pulses, depending on the type of

ADJUST potentiometer R202 is correctly set. The

equipment with which the recorder is used. For

fourth position, SIG., applies the radiosonde re-

ease of presentation, all wave forms shown on the

ceiver output signal to the cathode follower input.

simplified diagrams in this chapter are taken with

b. The input signal voltage is applied across

SIGNAL SELECTOR switch S202 in the 120 CPS

position. The input test signal in this instance is

resistor R301 and through de blocking capacitor

the 120-cycle ripple voltage taken from the nega-

C301 to the grid of tube V301A. The plate is con-

nected directly to the low impedance 300-volt posi-

tive power supply ahead of the filter; the shape of

the wave is between a sawtooth and sine. The 60

tive supply. Voltage-dividing resistors R304 and

R305 reduce the positive potential to a nominal

cps test voltage is a sine wave taken directly from

140 volts for use as a "bias potential for the grid

the power transformer in the power supply.

Figure 21. Cathode follower and noise-suppression diode,

simplified schematic diagram.

2-3