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參數(shù)資料
| 型號： | VCA610 |
| 英文描述： | WIDEBAND VOLTAGE CONTROLLED AMPLIFIER |
| 中文描述： | 寬帶電壓控制放大器 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 212K |
| 代理商： | VCA610 |
VCA610
6
APPLICATIONS INFORMATION
CIRCUIT DESCRIPTION
The VCA610 is a wideband voltage amplifier with a
voltage-controlled gain, as modeled in Figure 1. The
circuit’s basic voltage amplifier responds to the control
of an internal gain control amplifier. At its input, the
voltage amplifier presents the high impedance of a dif-
ferential stage, permitting flexible input impedance matching.
To preserve termination options, no internal circuitry
connects to the input bases of this differential stage. For
this reason, the user should provide DC paths for the
input base currents either through a grounded termina-
tion resistor or a direct connection to ground. The differ-
ential input stage also permits rejection of common-
mode signals to remove ground bounce effects. At its
output, the voltage amplifier presents the low impedance
of class A-B emitter-follower stage, again simplifying
impedance matching. An open-loop design produces wide
bandwidth at all gain levels and avoids the added over-
load-recovery and propagation delays of feedback de-
signs. Repeated use of differential stages minimizes off-
set effects for reduced feedthrough of the gain control
signal. A ground-sensing, differential to single-ended
converter retains the low offset in the amplifier output
stage.
to +40dB range as V
C
varies from 0 to –2V. Optionally,
making V
C
slightly positive,
≥
0.1V, effectively disables the
amplifier, giving 80dB of attenuation at low frequencies.
Internally, the gain control circuit varies the amplifier gain
through a time-proven method which exploits the linear
relationship between the transconductance, g
m
, of a bipolar
transistor and the transistor’s bias current. Varying the bias
currents of differential stages varies g
m
to control the voltage
gain of the VCA610. Relying on transistor g
m
to set gain also
avoids the need for a noise-producing gain-set resistor in the
amplifier input circuit. This reliance normally introduces a
high thermal sensitivity to the gain. However, the VCA610
employs specialized analog signal processing that removes
this thermal effect.
INPUT/OUTPUT RANGE
The VCA610’s 80dB gain range allows the user to handle an
exceptionally wide range of input signal levels. If the unit’s
input and output voltage range specifications are exceeded,
however, signal distortion and amplifier overloading will
occur. The VCA610’s maximum input and output voltage
range is best illustrated in Figure 2.
Gain Control
Circuit
Voltage
Amplifier
Gain Control
Amplifier
V
O
V–
GND
V+
–In
+In
V
C
FIGURE 1. Block Diagram of the VCA610.
A user-applied voltage, V
C
, controls the amplifier’s gain
magnitude through a high-speed control circuit. Gain polar-
ity can be either inverting or noninverting depending upon
the amplifier input driven by the input signal. Use of the
inverting input is recommended since this connection tends
to minimize positive feedback from the output to the non-
inverting input. The gain control circuit presents the high
input impedance of a noninverting op amp connection.
Control voltage V
C
varies the amplifier gain according to the
exponential relationship G(V/V) = 10
–2 (Vc +1)
. This trans-
lates to the linear, logarithmic relationship G(dB) = – 40 –
40V
C
. Thus, G(dB) varies linearly over the specified –40dB
Figure 2 plots output power vs input power for five voltage
gains spaced at 20dB intervals. The 1dBm compression
points occur where the actual output power (solid lines)
deviates by –1dBm from the ideal output power (dashed
lines). Compression is produced by different mechanisms
depending on the selected gain. For example, at G = –40dB,
1dBm compression occurs when the input signal approaches
approximately 3Vp-p (13.5dBm for R
S
= 50
). Input over-
loading is the compression mechanism for all gains from
–40dB to about –5dB. For gains between –5dB and +5dB,
the compression is due to internal gain stage overloading.
Compression over this gain range occurs when the output
signal becomes distorted as internal gain stages become
overdriven. At G = 0dB, 1dBm compression occurs when
the input exceeds approximately 1.5Vp-p (7.5dBm). At
gains greater than about 5dB, the compression mechanism is
due to output stage overloading. Output overloading occurs
FIGURE 2. Input and Output Range.
OUTPUT POWER vs INPUT POWER
Input Power in dBm (Differential Input Voltage in Vp-p)
+10
0
–10
–20
–30
–40
–50
–60
–60
(6E-4)
O
6.33
3.0
2.0
V
O
–50
(0.002)
–40
(0.006)
–30
(0.02)
–20
(0.063)
–10
(0.2)
0
(0.63)
+10
(2)
+20
(6.3)
0.633
0.20
0.063
0.02
6E-3
2E-3
G = –40dB
G = –20dB
G = 0dB
G = +20dB
G = +40dB
CoPoints
Ideal
—
Actual
+
+
+
+
+
+(3Vp-p)
R
s
= 50
R
= 500
f = 1MHz
相關PDF資料 |
PDF描述 |
|---|---|
| VCA610P | WIDEBAND VOLTAGE CONTROLLED AMPLIFIER |
| VCA610PA | WIDEBAND VOLTAGE CONTROLLED AMPLIFIER |
| VCA610U | WIDEBAND VOLTAGE CONTROLLED AMPLIFIER |
| VCA610UA | WIDEBAND VOLTAGE CONTROLLED AMPLIFIER |
| VCA810 | High Gain Adjust Range, Wideband, Voltage-Controlled Amplifier |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| VCA610P | 制造商:BB 制造商全稱:BB 功能描述:WIDEBAND VOLTAGE CONTROLLED AMPLIFIER |
| VCA610PA | 制造商:BB 制造商全稱:BB 功能描述:WIDEBAND VOLTAGE CONTROLLED AMPLIFIER |
| VCA610U | 功能描述:IC OPAMP VGA R-R 30MHZ SGL 8SOIC RoHS:否 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 產(chǎn)品變化通告:Discontinuation 18/May/2012 標準包裝:2,000 系列:- 放大器類型:通用 電路數(shù):4 輸出類型:滿擺幅 轉換速率:0.42 V/µs 增益帶寬積:1.5MHz -3db帶寬:- 電流 - 輸入偏壓:15nA 電壓 - 輸入偏移:1000µV 電流 - 電源:116µA 電流 - 輸出 / 通道:100mA 電壓 - 電源，單路/雙路(±):1.8 V ~ 5 V，±0.9 V ~ 2.5 V 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:14-TSSOP（0.173"，4.40mm 寬） 供應商設備封裝:14-TSSOP 包裝:帶卷 (TR) 產(chǎn)品目錄頁面:851 (CN2011-ZH PDF) 其它名稱:296-20930-2 |
| VCA610UA | 制造商:BB 制造商全稱:BB 功能描述:WIDEBAND VOLTAGE CONTROLLED AMPLIFIER |
| VCA-6303 | 制造商:Quest Technology International Inc 功能描述: |
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