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參數(shù)資料
| 型號： | OPA678 |
| 英文描述： | Wideband Switched-Input OPERATIONAL AMPLIFIER |
| 中文描述： | 寬帶開關(guān)輸入運算放大器 |
| 文件頁數(shù)： | 7/14頁 |
| 文件大?。?/td> | 279K |
| 代理商： | OPA678 |
OPA678
7
A
Select
A
Select
–
Q7
Q8
Q1
Q2
A
Q3
Q4
B
+ –
+
Q5
Q6
+V
CC
Bias
Comp
I
TAIL
–V
CC
Out
THEORY OF OPERATION
The simplified circuit of the ECL compatible OPA678 is
shown in Figure 1. It is a “classical” high-speed op amp
architecture with one important exception—the amplifier
has two ECL logic selectable differential input stages. An
appropriate differential ECL logic signal on A and A will
turn on either Q5 or Q6, steering operating (tail) current to
either differential input pair Q1 and Q2 or Q3 and Q4. The
input pair receiving the tail current operates as a conven-
tional op-amp input stage while the de-selected input pair
receiving no tail current appears as an open circuit. The de-
selected inputs have only a few pF parasitic capacitance and
in the off condition exhibit only a very low leakage (bias)
current of about 100pA. Two feedback networks can be
connected to each input separately allowing a wide range of
circuit applications. The feedback network connected to the
selected input operates in a normal op amp fashion while the
feedback network connected to the de-selected input is
totally inactive, appearing only as an additional load to the
amplifier’s output stage.
For TTL operation, “A select” is held to an internal refer-
ence level by tying pins 13 and 14 together. This allows “A”
to become the single-ended TTL input.
FIGURE 1. OPA678 Simplified Circuit Diagram.
Standard TTL and ECL logic levels may be applied to each
input selection circuit but only 350mV is typically required
to switch between inputs. This logic input sensitivity allows
simpler high-speed logic driver circuitry and it minimizes
digital noise coupling into adjacent wideband analog cir-
cuitry and allows single ended ECL inputs to be used with
V
BB
applied to the other input.
The OPA678 is designed to be frequency compensated by a
single capacitor connected from pin 5 to ground. Recom-
mended compensation is shown in
the Typical Performance
Curve section. A small variable capacitor may be trimmed
for best bandwidth, settling time, and gain peaking. Closed-
loop gain/phase (Bode) plots are shown in the Typical
Performance Curves.
OFFSET TRIM
The laser trimmed input offset voltage is low enough for
many video and RF applications. Independent control of
input offset will require that trim adjust current be summed
into one or both inputs.
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| OPA680U | Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable TM |
| OPA680 | Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable TM |
| OPA680N | Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable TM |
| OPA680P | Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable TM |
| OPA681U | Wideband, Current Feedback OPERATIONAL AMPLIFIER With Disable |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA678AP | 制造商:BB 制造商全稱:BB 功能描述:Wideband Switched-Input OPERATIONAL AMPLIFIER |
| OPA678AU | 功能描述:高速運算放大器 Widebane Switched RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| OPA680 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable |
| OPA680N | 制造商:BB 制造商全稱:BB 功能描述:Wideband, Voltage Feedback OPERATIONAL AMPLIFIER With Disable TM |
| OPA680N/250 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Voltage-Feedback Operational Amplifier |
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