EL2003, EL2033Parallel Operation IOUT ≥ ±300mA ROUT 2 Ω BW 100MHz SR = 1000V/µsJ1, J2 2N5911 Dual FET R1, R2 Offset AdjustRL = 100 Ω , CL = 10pF, VS = ±15V Top is VIN, Bottom is VOUTLARGE SIGNAL RESPONSECapacitive Loads The EL2003 and EL2033 are stable driving any type of FET INPUT BUFFER WITH HIGH OUTPUT CURRENTS capacitive load. However, when driving a pure capacitance of less than a thousand picofarads the frequency response Resistive Loads has excessive peaking as shown in the characteristic curves. The DC gain of the EL2003 and EL2033 is the product of the The squarewave response will have large overshoots and unloaded gain (0.995) and the voltage divider formed by the will ring for several hundred nanoseconds. device output resistance and the load resistance. If the peaking and ringing cause system problems they can RL be eliminated with an RC snubber circuit from the output to A = 0.995 × --------------- V R + R L OUT ground. The values can be found empirically by observing a squarewave or the frequency response. First just put the The high frequency response of the EL2003 and EL2033 resistor alone from output to ground until the desired varies with the value of the load resistance as shown in the response is obtained. Of course the gain will be reduced due characteristic curves. If the 100MHz peaking is undesirable to ROUT. Then put capacitance in series with the resistor to when driving load resistors greater than 50Ω, an RC snubber restore the gain at low frequencies. Start with a small circuit can be used from the output to ground. The snubber capacitor and increase until the response is optimum. Too circuit works by presenting a high frequency load resistance large a capacitor will roll the gain off prematurely and result of less than 50Ω while having no loading effect at low in a longer settling time. The figure below shows an example frequencies. of an EL2003 driving a 330pF load, which is similar to the input of a flash converter. RL = 50 Ω , CL = 10pF, VS = ±15V Top is VIN, Bottom is VOUTSMALL SIGNAL RESPONSE 6
