Datasheet
LT1010
11
1010fe
APPLICATIONS INFORMATION
The 50Ω video line splitter here puts feedback on one
buffer with the others slaved. Offset and gain accuracy of
slaves depend on their matching with master.
When driving long cables, including a resistor in series
with the output should be considered. Although it reduces
gain, it does isolate the feedback amplifier from the effects
of unterminated lines which present a resonant load.
When working with wideband amplifiers, special attention
should always be paid to supply bypassing, stray capaci-
tance and keeping leads short. Direct grounding of test
probes, rather than the usual ground lead, is absolutely
necessary for reasonable results.
The LT1010 has slew limitations that are not obvious
from standard specifications. Negative slew is subject
to glitching, but this can be minimized with quiescent
current boost. The appearance is always worse with fast
rise signal generators than in practical applications.
Track and Hold
The 5MHz track and hold shown here has a 400kHz power
bandwidth driving ±10V. A buffered input follower drives
the hold capacitor, C4, through Q1, a low resistance FET
switch. The positive hold command is supplied by TTL
logic with Q3 level shifting to the switch driver, Q2. The
output is buffered by A3.
When the gate is driven to V
–
for HOLD, it pulls charge
out of the hold capacitor. A compensating charge is put
into the hold capacitor through C3. The step into hold is
made independent of the input level with R7 and adjusted
to zero with R10.
Since internal dissipation can be quite high when driving
fast signals into a capacitive load, using a buffer in a power
package is recommended. Raising buffer quiescent current
to 40mA with R3 improves frequency response.
This circuit is equally useful as a fast acquisition sample
and hold. An LT1056 might be used for A3 to reduce drift
in hold because its lower slew rate is not usually a problem
in this application.
Current Sources
A standard op amp voltage to current converter with a
buffer to increase output current is shown here. As usual,
A3
LT1010
A2
LT1010
R2
200Ω
R1
50Ω
R3
800Ω
R4
39Ω
R5
39Ω
C1
20pF
INPUT
1010 AI11
OUTPUT 1
OUTPUT 2
–
+
A1
HA2625
OTHER
SLAVES
A2
LT1010
–
+
–
+
A3
LT118A
A4
LT118A
C1
50pF
C2
150pF
HOLD
R2
2k
D1
HP2810
Q3
2N2907
V
–
Q1
2N5432
S D
R4
2k
Q2
2N2222
R8
5k
R9
10k
D2*
6V
*2N2369 EMITTER BASE JUNCTION
OUTPUT
R10
50k
R5
1k
R6
1k
C4
1nF
C3
100pF
C5
10pF
R1
2k
R3
20Ω
INPUT
V
+
–
+
A1
LT118A
R11
6.2k
1010 AI12
R7
200k