CORPORATION a Triple 140MHz High Output Voltage CRT Driver FEATURES @ Bandwidth 0.0.0... eee cece eee 140MHz @ Rise/Fall Time. 0.00... cece cee ae 3.6ns @ Swing Upto .... 0... cece cece ee eee 65 Vp-p @ Supply Voltage... eee eee eee eee 80V @ Pin to Pin Compatible with CVA2426, CVA2427, CR5527 APPLICATIONS @ CRT Driver for 1600 x 1280 and 1280 x 1024 Color Monitors CVA2438 DESCRIPTION The CVA2438 contains three video driver amplifiers designed specially to drive high resolution color monitors. With such high output voltage and excellent AC performance, this device will provide excellent drive capability for high resolution larger screen color monitors. ORDERING INFORMATION Part Package CVA2438S CY12B Temperature -20C to +90C CONNECTION DIAGRAM AND SIMPLIFIED SCHEMATIC rH] ul aps] wl of nf @] of of -| ceecroaoognma a + Z2QF + or tZaOe $2253 7253 225 o 9 GO o 0 1A 39 13 CVA2438 GND 9 3,7,11 1A-49 MB 1844322 0001184 637 3-65 CVA2438 ABSOLUTE MAXIMUM RATINGS CORPORATION a Supply Voltage = Vs - Vout(min) < 80V and Vourmay < 80V Lead Temperature ........-0- 000 c eee eee eee +300C Operating Temperature ..........-.5-0-- -20C to +90C Storage Temperature.........--.-.606. -25C to +100C DC ELECTRICAL CHARACTERISTICS Vs = 85V, Vout = 60Vp-p, Tease = +25C, See Figure 1. SYMBOL CHARACTERISTICS MIN TYP MAX UNITS loc Supply Current 29 35 mA Vinoc Input DC Level 1.3 1.6 1.9 Voutoc Output DC Level 35 42.5 48 Av Voltage Gain 13 15 17 Gain Matching 0.2 dB AC ELECTRICAL CHARACTERISTICS Vs = 85V, Vout = 60Vp-p, Tcase = +25C. See Figure 1. SYMBOL CHARACTERISTICS MIN TYP MAX UNITS tr Rise Time 3.6 5.0 ns ig Fall Time 3.6 5.0 ns BW Bandwidth 140 MHz Le Linearity 5 % Os Overshoot 5 % us Undershoot 5 % FIGURE 1. TEST CIRCUIT INPUT o R1=5102 C1 = Variable 4 to 150pF C4 = 10pt/160V O01 = DS464 R2 = 5602 Typical 27pF C6 = 0.01 pf/160V D2 = DS464 R3 = 10kQ C2 = Variable 4 to 150pF C, = 8pF (Including L1 = 390nH R4=51kQ Typical 17pF Parasitics) R5=152 C3 = 104pF RG = 229 4A-50 Mi 18443ee 0001185 573 3-66 CORPORATION a APPLICATIONS INFORMATION Basic Circuit Configuration The CVA2438 is an transimpedance amplifier with two stage feedback amplifier configurations. Any change in input current will be reflected as change in output voltage swing. A resistor in series with the input will change the CVA2438 into a voltage amplifier. The output is an emitter follower, Because of the complementary circuitry employed, there is no need for load or pull up resistor. An internally bypassed capacitor is included inside the package, however, for low frequencies an electrolytic capacitor is recommended. CVA2438 has an internal feedback resistor of 11KQ as shown in Figure 3. In the absence of any input signal, the Vout DC is set by R Vout (DG) = (1 + A) Vin (DC) If an input signal is applied, the gain is set by R Vout = Ge) Vin Input and Transfer Characteristics An input current swing of +5.0mA causes the output to change by t30V. A resistor of 680Q In series with the input will give a voltage gain of -13. CVA2438 Output Characteristics CVA2438 Is intended to be used as the final stage of very fast video circuits. The nominal load capacitance is 10pF. Other values can be accommodated since the output stage is an emitter follower and is fairly insensitive to load capacitance. However, a wire connection of some length is unavoidable, that causes objectionable ringing due to a resonant circuit. To avoid this a damping resistor must be used in series with the lead inductance. Also a resistor is necessary to protect the amplifier against arching. A resistor of 50-1000 will provide protection but will slow down the response. The lead inductance may be artificially increased by a tenth of a microHenry to obtain desired peak. Any change in inductance will require readjustment of damping resistor, as stated by equation (1). rave ay The output of CVA2438 is not short circuit proof. Any resistance to V+ or Ground should be >6002. Thermal Characteristics When low frequency square waves are amplified, some droop will occur due to a large change in thermal dissipation in the input transistors. To overcome this an R-C series feedback network is suggested with 51kQ and 62pF values. Under normal operating conditions the CVA2438 will dissipate up to 14W. The maximum allowed case temperature is +90C. To calculate maximum heatsink thermal resistance use equation (2). {90 50) Input pins are internal de feedback nodes and thus have iow Rth = =2.66C/W impedances. These pins must be fed from a series AC 15W network for high frequency emphasis. Figure 2 shows several appropriate networks for design aides. FIGURE 2. 6800 We a=) Vout A ~17pF b [\b< 65V 6800 a ny b) @ a ~270F seg = Ww a oO ft a Q O co) L = 27pF 5 150 wale 5 15V 1 L i 1 L i B00 4 5 10 15 20 25 30 t a) TIME (ns) ~17pF ~ MB 1844322 0001146 4OT 3-67 CVA2438 C al og C BANDWIDTH FALL TIME RISE TIME GAIN 8dB/DIV VOLTS 1OV/DIV VOLTS 10V/DIV 5ns/DIV 5ns/DIV MHz 18-01 18-02 18-09 MB 18443cee 0001187 345 3-68