10

acceptable with the Metal-Film resistors giving slightly less

peaking and bandwidth because of additional series

inductance. Use of sockets, particularly for the SO package,

should be avoided if possible. Sockets add parasitic

inductance and capacitance which will result in additional

peaking and overshoot.

Disable/Power-Down

The EL5164 amplifier can be disabled placing its output in a

high impedance state. When disabled, the amplifier supply

current is reduced to < 150µA. The EL5164 is disabled when

its CE pin is pulled up to within 1V of the positive supply.

Similarly, the amplifier is enabled by floating or pulling its CE

pin to at least 3V below the positive supply. For ±5V supply,

this means that an EL5164 amplifier will be enabled when

CE is 2V or less, and disabled when CE is above 4V.

Although the logic levels are not standard TTL, this choice of

logic voltages allows the EL5164 to be enabled by tying CE

to ground, even in 5V single supply applications. The CE pin

can be driven from CMOS outputs.

Capacitance at the Inverting Input

Any manufacturer’s high-speed voltage- or current-feedback

amplifier can be affected by stray capacitance at the

inverting input. For inverting gains, this parasitic capacitance

has little effect because the inverting input is a virtual

ground, but for non-inverting gains, this capacitance (in

conjunction with the feedback and gain resistors) creates a

pole in the feedback path of the amplifier. This pole, if low

enough in frequency, has the same destabilizing effect as a

zero in the forward open-loop response. The use of large-

value feedback and gain resistors exacerbates the problem

by further lowering the pole frequency (increasing the

possibility of oscillation.)

The EL5164, EL5165, and EL5364 have been optimized

with a TBD

Ω feedback resistor. With the high bandwidth of

these amplifiers, these resistor values might cause stability

problems when combined with parasitic capacitance, thus

ground plane is not recommended around the inverting input

pin of the amplifier.

Feedback Resistor Values

The EL5164, EL5165, and EL5364 have been designed and

value of feedback resistor gives 300MHz of -3dB bandwidth

gives 275MHz of bandwidth with 1dB of peaking. Since the

EL5164, EL5165, and EL5364 are current-feedback

more bandwidth. As seen in the curve of Frequency

can be easily modified by varying the value of the feedback

resistor.

Because the EL5164, EL5165, and EL5364 are current-

feedback amplifiers, their gain-bandwidth product is not a

constant for different closed-loop gains. This feature actually

allows the EL5164, EL5165, and EL5364 to maintain about

the same -3dB bandwidth. As gain is increased, bandwidth

decreases slightly while stability increases. Since the loop

stability is improving with higher closed-loop gains, it

specified TBD

Ω and still retain stability, resulting in only a

slight loss of bandwidth with increased closed-loop gain.

Supply Voltage Range and Single-Supply

Operation

The EL5164, EL5165, and EL5364 have been designed to

operate with supply voltages having a span of greater than

5V and less than 10V. In practical terms, this means that

they will operate on dual supplies ranging from ±2.5V to ±5V.

With single-supply, the EL5164, EL5165, and EL5364 will

operate from 5V to 10V.

As supply voltages continue to decrease, it becomes

necessary to provide input and output voltage ranges that

can get as close as possible to the supply voltages. The

EL5164, EL5165, and EL5364 have an input range which

extends to within 2V of either supply. So, for example, on

±5V supplies, the EL5164, EL5165, and EL5364 have an

input range which spans ±3V. The output range of the

EL5164, EL5165, and EL5364 is also quite large, extending

to within 1V of the supply rail. On a ±5V supply, the output is

therefore capable of swinging from -4V to +4V. Single-supply

output range is larger because of the increased negative

swing due to the external pull-down resistor to ground.

Video Performance

For good video performance, an amplifier is required to

maintain the same output impedance and the same

frequency response as DC levels are changed at the output.

This is especially difficult when driving a standard video load

of 150

Ω, because of the change in output current with DC

level. Previously, good differential gain could only be

achieved by running high idle currents through the output

transistors (to reduce variations in output impedance.)

These currents were typically comparable to the entire

5.5mA supply current of each EL5164, EL5165, and EL5364

amplifiers. Special circuitry has been incorporated in the

EL5164, EL5165, and EL5364 to reduce the variation of

output impedance with current output. This results in dG and

dP specifications of TBD% and TBD°, while driving 150

Ω at

a gain of 2.

Video performance has also been measured with a 500

Ω

load at a gain of +1. Under these conditions, the EL5164,

EL5165, and EL5364 have dG and dP specifications of

0.01% and 0.01°, respectively.

Output Drive Capability

In spite of their low 5.5mA of supply current, the EL5164,

EL5165, and EL5364 are capable of providing a minimum of

±75mA of output current. With a minimum of ±75mA of

output drive, the EL5164, EL5165, and EL5364 are capable

of driving 50

Ω loads to both rails, making it an excellent

EL5164, EL5165, EL5364