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OPA2836 View Datasheet(PDF) - Texas Instruments

Part NameDescriptionManufacturer
OPA2836 Very-Low-Power, Rail-to-Rail Out, Negative Rail In, Voltage-Feedback Operational Amplifiers TI
Texas Instruments TI
OPA2836 Datasheet PDF : 59 Pages
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www.ti.com
Feature Description (continued)
OPA836, OPA2836
SLOS712I – JANUARY 2011 – REVISED OCTOBER 2016
24
21
VS = 5 V,
VOUT = 100
mVpp,
18 G = 2,
RL = 1 kW
15
RF = 100 kW
12
RF = 100 kW
9
CF = 1 pF
RF = 10 kW
RF = 10 kW
CF = 1 pF
6
RF = 1 kW
3
0
-3
-6
-9
0
1
10
100
1000
f - Frequency - MHz
Figure 55. Frequency Response With Various Gain-Setting Resistor Values
As expected, larger value gain resistors cause lower bandwidth and peaking in the response (peaking in the
frequency response is synonymous with overshoot and ringing in the pulse response). Adding 1-pF capacitors in
parallel with RF helps compensate the phase margin and restores flat frequency response. Figure 56 shows the
test circuit.
VIN
RG
OPA 836
VOUT
1 kW
RF
CF
Figure 56. G = 2 Test Circuit for Various Gain-Setting Resistor Values
8.3.5 Driving Capacitive Loads
The OPA836 and OPA2836 devices can drive up to a nominal capacitive load of 2.2 pF on the output with no
special consideration. When driving capacitive loads greater than 2.2 pF, TI recommends using a small resister
(RO) in series with the output as close to the device as possible. Without RO, capacitance on the output interacts
with the output impedance of the amplifier causing phase shift in the loop gain of the amplifier that will reduce the
phase margin. This will cause peaking in the frequency response and overshoot and ringing in the pulse
response. Interaction with other parasitic elements may lead to instability or oscillation. Inserting RO will isolate
the phase shift from the feedback path and restore the phase margin; however, RO can limit the bandwidth
slightly.
Figure 57 shows the test circuit and Figure 43 shows the recommended values of RO versus capacitive loads,
CL. See Figure 40 for the frequency response with various values.
VIN
OPA836
RO
CL
VOUT
1 kW
Figure 57. RO versus CL Test Circuit
Copyright © 2011–2016, Texas Instruments Incorporated
Product Folder Links: OPA836 OPA2836
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