BUF600 Datasheet, PDF (9/14 Pages) Burr-Brown (TI) – HIGH-SPEED BUFFER AMPLIFIER

TYPICAL PERFORMANCE CURVES (CONT)
At V_CC = ±5V, R_LOAD = 100Ω (BUF601), R_LOAD = 200Ω (BUF600), and T_A = 25°C, unless otherwise noted.
BUF600, BUF601 GAIN ERROR vs INPUT VOLTAGE
5
(Full Temperature Range, R_LOAD = 10kΩ)
4
BUF600
3
2
1
BUF601
0
–5 –4 –3 –2 –1 0 1 2 3 4 5
Input Voltage (V)
I_Q vs TIME (Warmup)
100
99
BUF600
98
BUF601
97
96
95
94
0
1
2
3
4
5
6
7
8
Time (s)
DISCUSSION OF
PERFORMANCE
The BUF600 and BUF601 are fabricated using a high-
performance complementary bipolar process, which
variations in source impedances. A resistor between 100Ω
and 250Ω in series with the buffer input lead will usually
provides high-frequency NPN and PNP transistors with eliminate oscillation problems from inductive sources such
gigahertz transition frequencies (f_Τ). Power supplies are
rated at ±6V maximum, with the data sheet parameters
specified at ±5V supplies. The BUF600 and BUF601 are
3-stage open-loop buffer amplifiers consisting of comple-
mentary emitter followers with a symmetrical class AB
Darlington output stage. The complementary structure pro-
vides both sink and source current capability independent of
the output voltage, while maintaining constant output and
input impedances. The amplifiers use no feedback, so their
low-frequency gain is slightly less than unity and somewhat
dependent on loading. The optimized input stage is respon-
sible for the high slew rate of up to 3600V/µs, wide large
signal bandwidth of 320MHz, and quiescent current reduc-
tion to ±3mA (BUF600) and ±6mA (BUF601). These
features yield an excellent large signal bandwidth/quiescent
current ratio of 320MHz, 5Vp-p at 3mA/6mA quiescent
as unterminated cables without sacrificing speed.
Another excellent feature is the output-to-input isolation
over a wide frequency range. This characteristic is very
important when the buffer drives different equipment over
cables. Often the cable is not perfect or the termination is
incorrect and reflections arise that act like a signal source at
the output of the buffer.
Open-loop devices often sacrifice linearity and introduce
frequency distortion when driving low load impedance. The
BUF600 and BUF601, however, do not. Their design yields
low distortion products. The harmonic distortion character-
istics into loads greater than 100Ω (BUF601) and greater
than 200Ω (BUF600) are shown in the Typical Performance
Curves. The distortion can be improved even more by
increasing the load resistance.
current. The complementary emitter followers of the input Differential gain (DG) and differential phase (DP) are among
stage work with current sources as loads. The internal PTAT the important specifications for video applications. DG is
power supply controls their quiescent current and with defined as the percent change in gain over a specified change
its temperature characteristics keeps the transconductance in output voltage level (0V to 0.7V.) DP is defined as the
of the buffer amplifiers constant. The Typical Performance phase change in degrees over the same output voltage
Curves show the quiescent current variation versus change. Both DG and DP are specified at the PAL subcarrier
temperature.
frequency of 4.43MHz. The errors for differential gain are
The cross current in the input stage is kept very low,
resulting in a low input bias current of 0.7µA/1.5µA and
high input impedance of 4.8MΩ || 1pF/2.5MΩ || 1pF. The
lower than 0.5%, while those for differential phase are lower
than 0.04°.
With its minimum 20mA long-term DC output current
second stage drives the output transistors and reduces the capability, 50mA pulse current, low output impedance over
output impedance and the feedthrough from output to input
when driving RLC loads.
frequency, and stability to drive capacitive loads, the BUF601
can drive 50Ω and 75Ω systems or lines. The BUF600 with
The input of the BUF600 and BUF601 looks like a high
resistance in parallel with a 1pF capacitance. The input
characteristics change very little with output loading and
input voltage swing. The BUF600 and BUF601 have excel-
lent input-to-output isolation and feature high tolerance to
lower quiescent current and therefore higher output imped-
ance is well-suited primarily to interstage buffering. This
type of open-loop amplifier is a new and easy-to-use step to
prevent an interaction between two points in complex high-
speed analog circuitry.
®
9
BUF600, 601