參數(shù)資料
型號: 5962-9469204QCA
廠商: TEXAS INSTRUMENTS INC
元件分類: 運算放大器
英文描述: QUAD OP-AMP, 1500 uV OFFSET-MAX, 0.73 MHz BAND WIDTH, CDIP14
封裝: CERAMIC, DIP-14
文件頁數(shù): 42/71頁
文件大?。?/td> 1709K
代理商: 5962-9469204QCA
TLC226x, TLC226xA
Advanced LinCMOS
RAIL-TO-RAIL
OPERATIONAL AMPLIFIERS
SLOS177D – FEBRUARY 1997 – REVISED MARCH 2001
47
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
APPLICATION INFORMATION
driving large capacitive loads
The TLC226x is designed to drive larger capacitive loads than most CMOS operational amplifiers. Figure 58
and Figure 59 illustrate its ability to drive loads greater than 400 pF while maintaining good gain and phase
margins (Rnull = 0).
A smaller series resistor (Rnull) at the output of the device (see Figure 62) improves the gain and phase margins
when driving large capacitive loads. Figure 58 and Figure 59 show the effects of adding series resistances of
10
, 20 , 50 , and 100 . The addition of this series resistor has two effects: the first is that it adds a zero
to the transfer function and the second is that it reduces the frequency of the pole associated with the output
load in the transfer function.
The zero introduced to the transfer function is equal to the series resistance times the load capacitance. To
calculate the improvement in phase margin, equation 1 can be used.
Θ
m1 + tan
–1
2
× π× UGBW × R
null ×
C
L
Where :
(1)
Θ
m1 + improvement in phase margin
UGBW
+ unity-gainbandwidthfrequency
R
null + output series resistance
C
L + load capacitance
The unity-gain bandwidth (UGBW) frequency decreases as the capacitive load increases (see Figure 60). To
use equation 1, UGBW must be approximated from Figure 60.
Using equation 1 alone overestimates the improvement in phase margin, as illustrated in Figure 61. The
overestimation is caused by the decrease in the frequency of the pole associated with the load, thus providing
additional phase shift and reducing the overall improvement in phase margin. The pole associated with the load
is reduced by the factor calculated in equation 2.
F
+
1
) gm × R
null
Where :
(2)
F
+ factor reducingfrequencyof pole
gm + small-signaloutput transconductance (typically 4.83 × 10
– 3 mhos)
R
null + output series resistance
For the TLC226x, the pole associated with the load is typically 7 MHz with 100-pF load capacitance. This value
varies inversely with CL: at CL = 10 pF, use 70 MHz, at CL = 1000 pF, use 700 kHz, and so on.
Reducing the pole associated with the load introduces phase shift, thereby reducing phase margin. This results
in an error in the increase in phase margin expected by considering the zero alone (equation 1). Equation 3
approximates the reduction in phase margin due to the movement of the pole associated with the load. The
result of this equation can be subtracted from the result of the equation in equation 1 to better approximate the
improvement in phase margin.
相關(guān)PDF資料
PDF描述
5962-9469204QDA QUAD OP-AMP, 1500 uV OFFSET-MAX, 0.73 MHz BAND WIDTH, CDFP14
5962-9469201Q2A DUAL OP-AMP, 3000 uV OFFSET-MAX, 0.73 MHz BAND WIDTH, CQCC20
5962-9469201QHA DUAL OP-AMP, 3000 uV OFFSET-MAX, 0.73 MHz BAND WIDTH, CDFP10
5962-9469201QPA DUAL OP-AMP, 3000 uV OFFSET-MAX, 0.73 MHz BAND WIDTH, CDIP8
5962-9469203Q2A DUAL OP-AMP, 1500 uV OFFSET-MAX, 0.73 MHz BAND WIDTH, CQCC20
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