Datasheet EL2002, EL2003 (Elantec) - 5

EL2003, EL2033 Applications Information Source Impedance
The EL2003 and EL2033 are monolithic buffer amplifiers The EL2003 and EL2033 have excellent input-output built with Elantec's proprietary dielectric isolation process isolation and are very tolerant of variations in source that produces NPN and PNP complimentary transistors. The impedances. Capacitive sources cause no problems at all, circuits are connection of symmetrical common collector resistive sources up to 100kΩ present no problems as long transistors that provide both sink and source current as care is used in board layout to minimize output to input capability independent of output voltage while maintaining coupling. Inductive sources can cause oscillations; a 1kΩ constant output and input impedances. The high slew rate resistor in series with the buffer input pin will usually and wide bandwidth of the EL2003 and EL2033 make them eliminate problems without sacrificing too much speed. An useful beyond video frequencies. unterminated cable or other resonant source can also cause oscillations. Again, an isolating resistor will eliminate the
Power Supplies
problem. The EL2003 and EL2033 may be operated with single or
Current Limit
split supplies as low as ±2.5V (5V total) to as high as ±18V (36V total). However, the bandwidth, slew rate, and output The EL2003 and EL2033 have internal current limits that impedance degrade significantly for supply voltages less protect the output transistors. The current limit goes down than ±5V (10V total) as shown in the characteristic curves. It with junction temperature rise as shown in the characteristic is not necessary to use equal value split supplies, for curves. At a junction temperature of +175°C the current example -5V and +12V would be excellent for 0V to 1V video limits are at about 100mA. If the EL2003 or EL2033 output is signals. shorted to ground when operating on ±15V supplies, the power dissipation will be greater than 1.5W. A heat sink is Bypass capacitors from each supply pin to a ground plane required in order for the EL2003 or EL2033 to survive an are recommended. The EL2003 and EL2033 will not indefinite short. Recovery time to come out of current limit is oscillate even with minimal bypassing, however, the supply about 250ns. will ring excessively with inadequate capacitance. To eliminate a supply ringing and the interference it can cause,
Heat Sinking
a 10µF tantalum capacitor with short pins is recommended When operating the EL2003 and EL2033 in elevated for both supplies. Inadequate supply bypassing can also ambient temperatures and/or high supply voltages and low result in lower slew rates and longer settling times. impedance loads, the internal power dissipation can force the junction temperature above the maximum rating (150°C
Input Range
for the plastic DIP). Also, an indefinite short of the output to The input to the EL2003 and EL2033 looks like a high ground will cause excessive power dissipation. resistance in parallel with a few picofarads in addition to a DC bias current. The input characteristics change very little The thermal resistance junction to case is 50°C/W for the with output loading, even when the amplifier is in current plastic DIP. A suitable heat sink will increase the power limit. However, there are clamp diodes from the input to the dissipation capability significantly beyond that of the package output that protect the transistor base emitter junctions. alone. Several companies make standard heat sinks for both These diodes start to conduct at about ±9.5V input to output packages. Aavid and Thermalloy heat sinks have been used differential voltage. Of course the input resistance drops successfully. dramatically when the diodes start conducting; the diodes
Parallel Operation
are rated at ±50mA. If more than 100mA output is required or if heat The input characteristics also change when the input voltage management is a problem, several EL2003 or EL2033s may exceeds either supply by 0.5V. This happens because the be paralleled together. The result is as though each device input transistor's base-collector junctions forward bias. If the was driving only part of the load. For example, if two units input exceeds the supply by LESS than 0.5V and then are paralleled then a 50Ω load looks like 100Ω to each returns to the normal input range, the output will recover in EL2003. Parallel operation results in lower input and output less than 10ns. However, if the input exceeds the supply by impedances, increased bias current but no increase in offset MORE than 0.5V, the recovery time can be hundreds of voltage. An example showing three EL2003s in parallel and nanoseconds. For this reason it is recommended that also the addition of a FET input buffer stage is shown below. schottky diode clamps from input to supply be used if a fast By using a dual FET the circuit complexity is minimal and the recovery from large input overloads is required. performance is excellent. Take care to minimize the stray capacitance at the input of the EL2003s for maximum slew rate and bandwidth. 5