EM A23型直流放大器是一种新的低噪声放大器，主要用于对灵敏的直流电进行测量、数据搜集和系统，对使用热耦合测量灵敏度而言十分理想。
A23的噪声等级与大约为25Ω的电阻器相当。
在进行温度测量时，与常规类型的热耦合共同使用时，可以达到大约10mK的灵敏度。输入电压偏移度很低，并且与灵敏度大约为1nV的电压兼容。
A23拥有许多测量放大器所需要的其他优点。高达100T或280dB的开环电压增益意味着可以使用由反馈电阻器精确控制的数值较高的总增益，因此能够在使用反馈电阻器定义的精确度的情况下，确保良好的线性。
虽然拥有较高的增益，A23型在100%反馈的情况下比较稳定，所以便可使用反馈电容器来过滤输出。输入信号等级的差异为±2mV，而输出差异±3mV。
A23的响应时间十分迅速，增益可以被统一降低至10kHz,即便在很高的增益设定情况下，都能确保良好的反应时间。
电源要求较低，大约为1.2mA，电压±6V，使其达到多管道测量系统的理想状态。根据设计，A23安装在一个打印的电路板上，使用一个规格为0.1英寸的栅格，在长度为1.6寸，宽度为1.2寸的长方形上设有13个管脚链接，安装在一个大尺寸高导磁率合金机箱内，可展现良好的磁性和静电性，对干扰具备较强的热免疫力。
打印电路板可以为电源提供链接、增益、滤波电容器和输出。它还能够对电压补偿和电流补偿进行控制、电源反耦合以及负的输出滤波，以减缓所有的调制副作用。
The EM DC Amplifier model A23 is a new 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 A23 is equivalent to a perfect resistor of about 25 ohms.
When used with normal type thermocouples for temperature measurement, sensitivities of around 10 micro-Kelvin can be achieved. The input voltage drift is very low and is compatible with voltage sensitivities of about 1 nanovolt.
The A23 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 A23 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 2 milli-volts and the output can be up to plus and minus 3 volts.
The response time of the A23 is fast, and the gain is reduced to unity at about 10 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 A23 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.
X=10 Seconds per Division Y = 1nV per Division
Measurement Rise Time Constant = 1 Second
图中：
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:电源过压
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
A23型直流放大器说明书
噪声
同等的噪声电阻大约为25Ω。峰峰噪声电压取决于选定的带宽，即：上升时间常数为1s，噪声电压大约为1.3nVp-p，输出功率大约等于250×10-6V，
Noise
Equivalent noise resistance approximately 25 ohms. Peak to peak noise voltage depends on bandwidth selected e.g. rise time constant 1 second, peak to peak noise voltage is approximately 1.3 nano-volts with the rms equivalent being about 250 pico-volts.
补偿电压
可以通过将电流引入终端反馈将补偿电压调整为0.内部反馈阻抗为1Ω，所以±100nA的调整电流将提供一个范围在±100nV的补偿电流。通过将百万Ω电压计在内部电源上连接，从而达成上述效果，设有11个和12个管脚，并将来自于刮片的5000万Ω阻抗与反馈连接第4管脚相连。补偿电压的温度系数通常为1nV/℃,不平衡补偿电压通常为±50nV。
Offset Voltage
This is adjustable to zero by introducing a current into the feedback terminal. The internal feedback resistor is 1 ohm and so an adjustment current of plus and minus 100 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 50M 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.
补偿电流
可以根据与补偿电压调节类似的方法将其调整为0，但在管脚6上使用一个10MΩ的阻抗。补偿电流的温度系数通常为2pA/℃。最初的不平衡电流通常为加减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100T或280dB。这一增益被统一减少为10KHz,速率为十进制的30dB。在100%反馈时，放大器是稳定的。
Gain and Bandwidth
Open loop voltage gain 100T or 280dB. This gain is reduced to unity at 10KHz, at a rate of 30dB per decade. The amplifier is stable with 100% feedback.
输入电阻
当输入电流为直流电时，电阻大于100MΩ。
Input Resistance
Greater than 100M ohm at DC
电源电阻
A23放大器严格遵循约翰逊噪声特性，其同等噪声阻抗大约在25Ω到2KΩ之间。在这一总体噪声区间内，A23噪声不会比自于电源的噪声大很多。当电源电阻为2K时，总体的噪声以每10年10dB的速度增加到高于电源噪声的程度，而噪声的总体增长大约为每10年20dB。当电源电阻低于25Ω时，噪声电阻将保持稳定，低至0Ω。
Source Resistance
The A23 closely follows the Johnson noise characteristic from its equivalent noise resistance (enr) of 25 ohms up to about 2K 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 2K, 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 25 ohms, the noise voltage is constant down to zero ohms.
输入等级
A23放大器将在± 20 mV的输入等级内运行。
Input Level
the A23 will operate with input levels up to +/- 20 mV.
输出等级
在直流电的情况下，A23将提供达到±3V的输出等级，并将输出±2mA电流。通过将输出电流最大化（来源于放大器输出），输出被限定在较低的增益中。因此，如果将增益设定为1，那么最大的输出等级与±2mV的最大输入等级相等同。最大输出的最低增益为1500。
Output Level
The A23 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 +/- 2mV. The minimum gain for maximum output is 1500.
反馈元件
当 a t.c.为15×10-6/℃，Ω值为1 ohm +/- 0.1%时，在与“反馈”终端和内部接地之间连接在内部反馈阻抗之上。通过将来源于“输出”的外部阻抗连接至“反馈”，从而对增益进行设定。阻抗值为： Rfb=（要求的增益-1）Ω，也就是：要求的增益=1000，rfb=999Ω。
Feedback Components
There is an internal feedback resistor connected to the 'Feedback' terminal and internal ground, of 1 ohm +/- 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 - 1) ohms. i.e. Gain required = 1000, Rfb = 999 ohms
连线
连接至A23的所有连线都有打印电路板管脚所构成，它们被配置在一个为0.1英寸的栅格上。该栅格位于一个长度为1.6英寸，宽度为1.2英寸的长方形中。pcb安装孔的直径应当为1毫米。
Connections
All connections to the A23 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.
电源
A23型放大器的电源为最低±5.5 V，最高±12V。
标称运行电源应当为±6V。
要求的电流为静止的1.5mA。
Power Supply
The A23 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.
规格
长度：2.12英寸 (53.8毫米), 宽度：1.62" (41.1毫米)
面板之上的高度0.75英寸（19毫米）
打印电路板管脚长度：0.22英寸（5.5毫米）
管脚规格：0.025平方英寸（0.64平方毫米）
重量：5.2盎司（149克）
可提供一个测试的电脑主板以安装A23型放大器。电压和电流补充控制的电源来自于内部管制电源。为电源、输入、反馈和已过滤或未过滤的输出进行链接。
主板尺寸：4.4英寸（112毫米）X 3.4英寸（82毫米）
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 A23, 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) |