EM直流放大器模块A22是为了高灵敏度测量和数据采集而设计的低噪声放大器组件，十分适合于热电偶的高灵敏度温度测量。
A22的噪声水平等价于150Ω电阻所产生的热噪声。
当使用A22对常规类型的热电偶进行温度测量时，可以获得20mK的灵敏度。A22具有极低的输入电压漂移，电压灵敏度约为1nV。
作为一个测量放大器，A22具有许多值得称赞的优点。它的开环电压增益高达100T（280dB），也即意味着通过负反馈可以获得高的闭环增益，这保证了放大器可以获得良好的线性度。线性度由反馈电阻精确控制。
尽管A22开环增益极高，但依然具有足够的稳定裕度，允许使用反馈电容来对输出信号滤波。输入信号范围为±20mV，输出范围可达±3V。
A22响应时间很短，在频率为20kHz时增益降低至单位1，这保证了即使在高闭环增益时放大器依然具有较短的响应时间。A22功耗极低，在±6V供电时静态供电电流仅为1.2mA，这使其十分适用于多通道测量系统。
A22可以通过13针的管脚安装在印制电路板上，管脚间距0.1英寸，安装尺寸为1.6× 1.2英寸。放大器密封在厚的高磁导率金属体中，这使A22具有良好的电磁屏蔽和热隔离效果。 印制电路板可以为A22提供包括供电、增益控制、滤波电容和输出连接等功能。它还可以实现对失调电压和电流的控制、电源线的去耦及调制信号的输出滤波。
The EM DC Amplifier model A22 is a low noise amplifier module for sensitive DC measurements, data collection and systems, and is ideal for very sensitive temperature measurement using thermocouples.
The noise level of the A22 is equivalent to a perfect resistor of about 150 ohms.
When used with normal type thermocouples for temperature measurement, sensitivities of around 20 micro-Kelvin can be achieved. The input voltage drift is very low and is compatible with voltage sensitivities of about 1 nanovolt.
The A22 has many other features desirable in a measurement amplifier. The very high loop voltage gain of 100T, or 280dB, means that high overall gain may be used, controlled precisely by feedback resistors, thus ensuring good linearity, with the accuracy defined by the feedback resistors used.
Despite the high gain, the model A22 is stable with 100% feedback, thus allowing feedback capacitors to be used to filter the output. The input signal level can be up to plus or minus 20 milli-volts and the output can be up to plus and minus 3 volts.
The response time of the A22 is fast, and the gain is reduced to unity at about 20 kHz, thus ensuring good response times, even at high gain settings.
The power supply requirement is low, being about 1.2 milli-amps with power supplies of plus and minus 6 volts, making it ideal for multi-channel measurement systems.
The A22 is designed to be mounted on a printed circuit board, using a 0.1&O5533; grid, with 13 pin connections on a rectangle 1.6&O5533; X 1.2&O5533;, and is built into a heavy gauge mumetal case which gives it very good magnetic, electrostatic and thermal immunity from interference. A printed circuit board is available which provides connections for power supply, gain, filter capacitors and outputs. It also contains controls for voltage and current offsets, power supply de-coupling and a passive output filter to reduce any modulation by-product.
图中：
All Dimensions in Inches:所有的尺寸以英寸计
DC AMPLIFIER A23：A23型直流放大器
A23 Connections:A23连接
Case：机箱
Input high: 高输入
Input low:低输入
Output：输出
Current Zero:电流零点
Case：机箱
Power Supply Ov:电源Ov
Power Supply Negative:负电源
Power Supply Positive:正电源
Internal Supply Negative:负内部电源
Internal Supply Positive:正内部电源
Case:机箱
A22型直流放大器说明
噪声
等效噪声电阻约为150Ω。噪声电压峰峰值取决于所选择的带宽。在稳定时间常数为1s时，噪声电压峰峰值约为3nV，均方根值约为600pV。 Noise
Equivalent noise resistance approximately 150 ohms. Peak to peak noise voltage depends on bandwidth selected e.g. rise time constant 1 second, peak to peak noise voltage is approximately 3 nano-volts with the rms equivalent being about 600 pico-volts
失调电压
通过引入电流至反馈端的方式可以将失调电压调节至零。内部反馈电阻为10Ω，因此当调节电流为±10nA时，可调节失调电压范围为±100nV。这可以通过在供电管脚（管脚11和12）之间连接1MΩ电阻、在电位器滑动片和反馈点（管脚4）之间连接500MΩ电阻实现。失调电压温度系数典型值为1nV/℃。初始失调电压典型值为±50nV。
Offset Voltage
This is adjustable to zero by introducing a current into the feedback terminal. The internal feedback resistor is 10 ohms and so an adjustment current of plus and minus 10 nano-amps will give a voltage offset in the range of plus and minus 100 nano-volts. This is achieved by connecting a 1 Meg-ohm potentiometer across the internal supply, pins 11 and 12 and connecting a 500M ohm resistor from the wiper to the feedback connection, pin 4. The temperature coefficient of offset voltage is typically 1 nV per degree C. The initial, unbalanced offset voltage is typically plus or minus 50nV.
失调电流
与失调电压调节方式相似，可以通过连接10MΩ电阻至6脚将失调电流调节至零。失调电流温度系数典型值为2pA/℃。初始失调电流典型值为±100pA。
Offset Current
This is adjustable to zero, in a similar manner to the offset voltage adjustment, but using a 10 M-ohm resistor to pin 6. The temperature coefficient of offset current is typically 2 pA per degree C. The initial, unbalanced offset current is typically plus or minus 100pA.
增益和带宽
开环电压增益为100T（280dB），随频率增大而以30dB/十倍频速度下降，在频率为20kHz时增益降低至单位1。在100%反馈时放大器稳定。 Gain and Bandwidth
Open loop voltage gain 100T or 280dB. This gain is reduced to unity at 20KHz, at a rate of 30dB per decade. The amplifier is stable with 100% feedback.
输入阻抗
直流时高于1GΩ。
Input Resistance
Greater than 1G ohm at DC.
源电阻
在源电阻为150Ω至10kΩ的范围内，A22遵循热噪声特性。且在这个范围内，总噪声仅比源噪声略为增加，每十倍频噪声增加10dB。在源电阻高于10kΩ时，噪声每十倍频增加10dB，因此总噪声每十倍频增加20dB。在源电阻低于150Ω时，电压噪声为常数。
Source Resistance
The A22 closely follows the Johnson noise characteristic from its equivalent noise resistance (enr) of 150 ohms up to about 10K ohms and in this range the total noise is very little more than the noise from the source alone, i.e. the noise increases by about 10dB per decade. At source resistance above about 10K, the overall noise increases above the source noise by about 10dB per decade, giving an overall increase of noise of about 20dB per decade. At source resistance below 150 ohms, the noise voltage is constant down to zero ohms.
输入电压
允许输入电压范围为±20mV。
Input Level
the A22 will operate with input levels up to +/- 20 mV.
输出电压
输出电压范围为±3V，输出电流为±2mA。在低增益设置时，从放大器输出的最大输出电流将限制输出电压范围。因此，如果增益设置为1，那么最大输出电压等于最大输入电压范围，即±20mV。若达到最大输出电压范围，增益不低于150倍。
Output Level
The A22 will provide an output level up to +/- 3 volts at DC and will deliver +/- 2 mA. The output is limited at low gain settings by the maximum output current which can be drawn from the amplifier output. Thus, if the gain is set to 1, the maximum output level is equivalent to the maximum input level of +/- 20mV. The minimum gain for maximum output is 150.
反馈元件
连接在反馈端和地之间的内部反馈电阻的阻值为10Ω、精度为1%、温度系数为15ppm/℃。闭环增益通过在输出端（管脚5）和反馈端（管脚4）连接的外部反馈电阻设置，阻值为Rfd=｛（增益×10）-10｝Ω。例如，要求增益为1000，那么反馈电阻应为9990Ω。
Feedback Components
There is an internal feedback resistor connected to the 'Feedback' terminal and internal ground, of 10 ohms +/- 0.1%, with a t.c. of 15ppm/degree C. The gain is set by connecting an external resistor from 'Output' to 'Feedback'. the value of this resistor is: Rfb = (gain required x 10) - 10 ohms. i.e. Gain required = 1000, Rfb = 9990 ohms.
连接
A22所有管脚均通过印制电路板连接。管脚间距0.1英寸，安装尺寸为1.6 1.2英寸。印制电路板安装孔直径应为1mm。
Connections
All connections to the A22 are made by printed circuit board pins, which are configured on a 0.1&O5533; grid, on a rectangle 1.6&O5533; X 1.2"&O5533;. The pcb mounting holes should be 1 mm diameter
供电
最小供电电压为±5.5V，最大供电电压为±12V，推荐供电电压为±6V，静态工作电流为1.5mA。
Power Supply
The A22 operates with supplies of +/- 5.5 volts minumum and +/- 12 volts maximum.
The nominal operating supply should be +/- 6 volts.
Current required is 1.5 mA quiescent.
尺寸
长度2.12英寸（53.8mm），宽度1.62英寸（41.1mm），高度0.75英寸（19mm）。
印制电路板管脚长度0.22英寸（5.5mm），管脚宽度0.025英寸（0.64mm）。
重量为5.2盎司（149g）。
用于安装A22的测试电路板具有以下功能：失调电压和失调电流调节，内部供电。管脚用于供电、输入、反馈、滤波/不滤波输出。电路板尺寸为4.4英寸（112mm） 3.4英寸（86mm）。
参数如有更改，恕不另行通知。
Dimensions
Length 2.12" (53.8mm), Width 1.62" (41.1mm)
Height above board 0.75" (19mm)
Printed Circuit Board Pin Length 0.22" (5.5mm)
Pin Size 0.025" (0.64mm) square.
Weight 5.2 ounces (149 gm)
A test pc board is available for mounting the A22, which has the following facilities. Voltage and current offset controls, powered from the internal regulated supplies. Pins for power supply, input, feedback and filtered or non-filtered outputs. Board Size 4.4" (112mm) x 3.4" (86mm)
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