Page 190 - The Art and Science of Analog Circuit Design

Tripping the Light Fantastic

Figure 11-33. ESSENTIALLY
GROUNDED
Field strength vs.
distance for a
ground referred HIGH
VOLTAGE
lamp. Field imbal-
ance promotes
uneven illumination
at low drive levels.

Figure 11-34. Placing a conductor along the lamp's length largely alleviates "thermome-
The "low tering." The trade-off is decreased efficiency due to energy leakage (see
thermometer" Note 4 and associated text). It is worth noting that various lamp types have
configuration. different degrees of susceptibility to the thermometer effect.
'Topside sensed" Some displays require an extended illumination range. "Thermome-
primary derived tering" usually limits the lowest practical illumination level. One
feedback balances acceptable way to minimize "thermometering" is to eliminate the large
lamp drive, extend-
ing dimming range.

C1=WIMAMKP-20
Q1, Q2 = ZETEX ZTX849 OR ROHM 2SC5001
L1 = COiLTRONICSCTX15Q-4
T1 = SUMIDAEPS-207
" = 1% FILM RESISTOR
0.03
*' = SELECT FOR INPUT COMMON MODE RANGE INCLUDES V !N
DO NOT SUBSTITUTE COMPONENTS
COILTRONICS {305} 781-8900, SUMIOA (708) 956-0666

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