EM 直流放大器模块A29

 

EM直流放大器模块A29是为了高灵敏度直流测量和数据采集而新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。A29的噪声水平等价于700Ω电阻所产生的热噪声，灵敏度为7nV，响应时间为1s。

当使用A29对常规类型的热电偶进行温度测量时，可以获得数百 mK的灵敏度。A29具有极低的输入电压漂移，电压灵敏度约为数nV。

作为一个测量放大器，A29具有许多值得称赞的优点。它的开环电压增益高达1T（240dB），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A29开环增益极高，但依然具有足够的稳定裕度，因而允许使用反馈电容来对输出信号滤波。输入信号范围为±2mV，输出范围可达±6V。

A29响应时间很短，在频率为300kHz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。A29功耗极低，在±12V供电时静态供电电流仅为3mA，这使其十分适用于多通道测量系统。

A29可以通过13针的管脚安装在印刷电路板上，管脚间距0.1英寸，安装尺寸为1.6×1.2英寸。放大器密封在不锈钢壳体中，这使A29具有电磁屏蔽和热隔离效果。

The EM DC amplifier model A29 is a low noise amplifier module, for sensitive DC measurements, data collection and systems, and is ideal for sensitive temperature measurement using thermocouples. The noise level of the A29 is equivalent to a perfect resistor of about 700 ohms, thus giving sensitivity of 7 nanovolts with a response time constant of a second. When used with normal type thermocouples for temperature

measurement, sensitivities of a few hundred micro Kelvin can be achieved. The input voltage drift is very low and is compatible with voltage sensitivities of a few nanovolts. The A29 has many other features desirable in a measurement amplifier. The very high loop voltage gain of

about 1T, or 240dB, 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.

Despite the high gain, the model A29 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 6 volts.

The response time of the A29 is fast, and the loop gain is reduced to unity at about 300 kHz, thus ensuring good response times, even at high gain settings.

The power supply requirement is low, being about 3 milli-amps with power supplies of plus and minus 12 volts, making it ideal for multi-channel measurement systems.

The A29 is designed to be mounted on a printed circuit board, using a 0.1" grid, with 13 pin connections on a dual in line rectangle 1.6" X 1.2", and is built into a stainless steel case which gives it immunity from interference both electrical and thermal.

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

A29型直流放大器说明

噪声

等效噪声电阻约为700Ω。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7nV（99%的时间），均方根值约为1.4nV。

Noise

Equivalent noise resistance approximately 700 ohms. Noise voltage depends on bandwidth selected, e.g. rise time constant 1 second, peak to peak noise voltage is approximately 7 nanovolts (for 99% of the time) with the rms equivalent being about 1.4 nanovolts.

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±100nA时，可调节失调电压范围为±1mV。这可以通过在供电管脚（管脚11和12）之间连接1MΩ电阻、在滑动片和反馈点（管脚4）之间连接100MΩ电阻实现。失调电压温度系数典型值为5nV/℃。取决于环境温度的变化速度，温度系数可能至10nV/℃。初始失调电压典型值为±500nV。

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 offset current of plus and minus 100 nano-amps will give a voltage offset in the range of plus and minus 1 microvolt. This is easily achieved by connecting a 1 Megohm potentiometer across the internal supply, pins 11 and 12, and connecting a 100 Mohm resistor from the wiper to the feedback connection, pin 4.

The temperature coefficient of offset voltage, DC, is typically 5 nV per degree C. There is also a differential temperature coefficient, up to 10 nV per degree C. depending on the rate of change of ambient temperature. This is negligable for normal environments, with a low rate of change. The initial, unbalanced offset voltage is typically plus or minus 500nV.

失调电流

初始失调电流典型值为±50pA。

失调电流温度系数典型值为2pA/℃。

Offset Current

The initial, unbalanced, offset current is typically 50pA.

The temperature coefficient of offset current is typically 2 pA per degree

源电阻

在源电阻从等效噪声电阻值至50kΩ的范围内，A29遵循热噪声特性。当源电阻在1kΩ至50kΩ的范围内，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50kΩ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1000Ω时，电压噪声为常数。放大器等效噪声电阻为700Ω。

Source Resistance

The A29 closely follows the Johnson noise characteristic from its equivalent noise resistance up to about 50K ohms. Between 1K ohms and 50K ohms source resistance, 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 50K, 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 1000 ohms, the noise voltage is constant down to zero ohms. 700 ohms is the amplifier equivalent noise resistance (enr).

输入电阻

直流时高于1GΩ。

Input Resistance

Greater than 1 Gohm, DC

增益和带宽

开环电压增益为1T（240dB），随频率增大而以30dB/十倍频速度下降，在频率为300kHz时增益降低至单位1。在100%反馈时放大器稳定。受限于此，流经10Ω反馈电阻的电流可取自输出级。

Gain and Bandwidth

Open loop voltage gain 1T or 240dB. This gain is reduced to unity at 300KHz, at a rate of 32dB per decade. The amplifier is stable with 100% feedback; the limitation to this is the current that can be taken from the output stage, which flows through the 10

ohm feedback resistor.

输入电压

允许输入电压范围为±2mV。

Input Level

The A29 will operate with input levels up to plus or minus 2 mV

输出电压

输出电压范围为±6V，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100，那么最大输出电压为±200mV。

Output Level

The A29 will provide an output level up to +/- 6 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 100, the maximum output level is 200mV.

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 25ppm/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.

Gain required = 1000, Rfb = 9.99K ohms.

连接

A29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 A29 are made by printed circuit board pins, which are configured on a 0.1" grid, on a rectangle 1.6" X 1.2". The pcb mounting hole should be 1 mm diameter.

供电

供电电压范围为±11V-±15V，推荐供电电压为±12V，静态工作电流为3mA。

Power Supply

The A29 operates from supplies of +/- 11 volts to +/- 15 volts. The nominal operating supply should be +/- 12 volts. Current required is +/- 3mA

尺寸

长度2.5英寸（61mm），宽度1.73英寸（44mm），高度0.69英寸（17.5mm）。

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3.3盎司（88g）。

Dimensions

Length 2.5" (61mm)

Width 1.73" (44mm)

Height above board 0.69" (17.5mm)

Printed Circuit Board Pin Length 0.22" (5.5mm)

Connection Pin Size 0.025" (0.64mm) square.

Weight

3.3 ounces (88 gm)

注意

通用PCB板可用于安装A29，PCB板上提供无源滤波、失调电压调节、供电管理等功能。

管脚用于输入、直接输出、滤波输出、反馈和滤波器连接。

电路板尺寸为3.5英寸×3英寸。

参数如有更改，恕不另行通知。

Note

A utility pc board is available for mounting the A29, which has a passive filter, which may be by-passed and the following facilities.

Voltage offset control, powered from the internal regulated supplies.

Pins for input, direct output, filtered output, power supply, feedback and filter connections.

Board Size 3.5" X 3"