LT1010_06 Datasheet, PDF (11/20 Pages) Linear Technology – Fast ±150mA Power Buffer

LT1010
APPLICATIO S I FOR ATIO
R3
800Ω
INPUT
C1
–
20pF
A1
HA2625
+
A2
LT1010
R4
39Ω
OUTPUT 1
R1 R2
50Ω 200Ω
A3
LT1010
R5
39Ω
OUTPUT 2
1010 AI11
OTHER
SLAVES
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 atten-
tion should always be paid to supply bypassing, stray
capacitance and keeping leads short. Direct grounding of
test probes, rather than the usual ground lead, is abso-
lutely 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 cur-
rent 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,
V⁺
R1
2k
INPUT
+
A1
LT118A
–
HOLD
C1
50pF
C2
150pF
R3
20Ω
A2
LT1010
Q1
2N5432
SD
R2
2k
D1
R4
C4
HP2810 _2k
1nF
R5
Q3
1k _2N2907
R6
1k
Q2
2N2222
C3
100pF
C5
10pF
R7
200k
–
A3
LT118A
+
A4
LT118A
R8
5k
V^–
*2N2369 EMITTER BASE JUNCTION
OUTPUT
D2*
6V
R9
10k
R10 _R11
50k _6.2k
1010 AI12
1010fc
11