NASA Electronic Parts and Packaging Program

**Operation of a Prototype Silicon-Germanium, Silicon-On-Insulator
Operational Amplifier**

**Type OPA211 Under Extreme Temperatures**

Richard Patterson, NASA Glenn Research Center, U.S.A.

Ahmad Hammoud, ASRC Aerospace / NASA GRC, U.S.A.

**Scope of Work**

A new prototype operational amplifier based on silicon germanium and
silicon-on-insulator technologies was recently introduced by Texas
Instruments, Inc. The OPA211 device is a low power, high speed precision
amplifier with rail-to-rail output swing capability and low noise \[1\].
It is rated for operation from -40 °C to +125 °C with a 30 mA output
current capability, and it can operate from a single or dual supply. The
amplifier can be used in applications such as signal processing,
filters, instrumentation, A/D drivers, and buffers for transducers.
Table I shows some of the device manufacturer's specifications.

Table I. Specifications of the OPA211 operational amplifier \[1\].

+------------------------------------------+---------------------------+
| ### Parameter (Unit)                     | ### Value                 |
+------------------------------------------+---------------------------+
| Supply Voltage (V)                       | +4.5 to +36 (single)      |
|                                          |                           |
|                                          | ±2.25 to ±18 (dual)       |
+------------------------------------------+---------------------------+
| Supply Current (mA)                      | 3.6                       |
+------------------------------------------+---------------------------+
| Output Current (mA)                      | 30                        |
+------------------------------------------+---------------------------+
| Bandwidth (MHz)                          | 80                        |
+------------------------------------------+---------------------------+
| Slew Rate (V/µs)                         | 27                        |
+------------------------------------------+---------------------------+
| Temperature Range (°C)                   | -40 to +125               |
+------------------------------------------+---------------------------+
| Package                                  | SO-8 plastic              |
+------------------------------------------+---------------------------+
| Lot \#                                   | POPA211AID                |
+------------------------------------------+---------------------------+

Since silicon germanium electronics are good at cryogenic temperatures
and their silicon-on-insulator counterparts are suited for high
temperatures, the OPA211 device has the potential for use in
applications where wide temperature swings, such as those of space
exploration missions, are anticipated. A circuit configured in an
inverting configuration was constructed utilizing the OPA211 chip and a
few passive components. The circuit was evaluated in the temperature
range between -195 °C to +140 °C in terms of signal gain and phase
shift, and supply current. These properties were recorded at selected
test temperatures in the frequency range of 1 kHz to 10 MHz. At each
test temperature, the device was allowed to soak for 15 minutes before
any measurements were made. A digital oscilloscope was used to capture
the waveforms of the input and output signals of the amplifier.
Cold-restart capability, i.e. power switched on while the device was at
cryogenic temperatures, was also investigated. In addition, the effects
of thermal cycling under a wide temperature range on the operation of
this high performance amplifier were determined. The circuit was exposed
to a total of 10 cycles between ‑195 °C and +140 °C at a temperature
rate of 10 °C/minute. Following the thermal cycling, circuit
measurements were then performed at the test temperatures of +25, -175,
and +140°C.

**Temperature Effects**

The gain of the amplifier at various test temperatures in the frequency
range of 1 kHz to 10 MHz is shown in Figure 1. It can be clearly seen
that the gain of the amplifier remained relatively the same, regardless
of the test temperature, until the test frequency of 2 MHz was reached.
Beyond that frequency, the gain exhibited changes in its magnitude and
roll-off frequency. For example, while the roll-off frequency was at 6.5
MHz at room temperature, it increased to about 7 MHz at the high
temperatures between +100 °C and +140 °C. Conversely, when exposed to
cryogenic temperatures, i.e. -100 °C to -175 °C, the roll-off frequency
of the gain fell in the range between 3 and 4 MHz. These changes are not
significant, and the drop in gain at very high frequencies is typical of
most operational amplifiers. In terms of temperature, therefore, the
amplifier circuit operated well in the temperature range between -175 °C
and +140 °C. Although temperature testing, as stated earlier, was to
include -195 °C, the results at that temperature revealed a harmonic
noise overriding both the input and the output signals. It is suspected
that the interference was introduced by the solenoid valve responsible
for delivering the liquid nitrogen inside the chamber rather than
temperature-induced effect on the operation of the circuit. Thus, these
results were excluded.

![](media/image1.wmf)

Figure 1. Gain versus frequency at various temperatures prior to thermal
cycling.

Figure 2 depicts the phase shift property of the amplifier as a function
of temperature and frequency. Similar to the gain characteristics, the
phase began to undergo slight and gradual decrease at about frequency of
2 MHz. Once again, these slight changes became more profound at the
cryogenic test temperatures, as evident by the slope of the phase
change.

![](media/image2.wmf)

Figure 2. Phase shift versus frequency at various temperatures prior to
thermal cycling.

**Cold Re-Start**

Cold-restart capability of the OPA211 amplifier was investigated at both
-175 °C and at -195 °C by allowing the circuit to soak at each of these
temperatures for at least 20 minutes without the application of supply
voltage or input signal. Power was then applied, and measurements were
taken on the output characteristics. The amplifier circuit was able to
successfully cold-restart at either of the two temperatures, and the
results obtained were similar to those obtained earlier at the
respective temperature.

**Effects of Thermal Cycling**

The effects of thermal cycling under a wide temperature range on the
operation of the OPA211 operational amplifier were investigated by
subjecting it to a total of 10 cycles between -195 °C and +140 °C at a
temperature rate of 10 °C/minute. The amplifier gain obtained after the
thermal cycling is shown in Figure 3 as a function of frequency at the
test temperatures of +140, +25, and -175 °C. It can be clearly seen that
these results were very similar to those obtained prior to cycling that
are depicted in Figure 1 and, thus, it can be concluded that the thermal
cycling had no effect on the amplifier's gain. Similarly, the phase
shift of the amplifier did not undergo much change with cycling, as
shown in Figure 4. In addition to maintaining its electrical performance
with cycling, the operational amplifier chip did not suffer any
deterioration or damage in its packaging due to this limited thermal
cycling.

![](media/image3.wmf)

Figure 3. Gain versus frequency at various temperatures after thermal
cycling.

![](media/image4.wmf)

Figure 4. Phase shift versus frequency at various temperatures after
thermal cycling.

The amplifier supply current was also recorded at various test
frequencies and temperatures. Current values obtained at the test
temperatures of +140, +25, and -175 °C for pre- and post-cycling
conditions are shown in Table II. The data reported are those obtained
at 1 MHz frequency. It can be seen that the supply current dropped with
decrease in temperature and increased slightly at high temperatures. As
far as cycling is concerned, no major change occurred in the supply
current, at any given temperature, as a result of the thermal cycling.

Table II. Supply current at various temperatures for pre- and
post-cycling conditions.

  ----------------------- ------------------------ -----------------------
                          **Pre-cycling**          **Post-cycling**

  **Temperature (°C)**    **Supply Current (mA)**  

  +140                    4.23                     4.26

  +25                     3.00                     3.04

  -175                    1.12                     1.14
  ----------------------- ------------------------ -----------------------

Waveforms of the input (blue curves) and the output (red curves) signals
of the amplifier were captured at 25, -175, and +140 °C prior to and
after the thermal cycling. These waveforms are depicted in Figures 5, 6,
and 7 at the test frequency of 100 kHz, 500 kHz, and 1 MHz,
respectively. It can be seen that while no variations were observed in
the amplifier's input and output signals at +140 °C, slight noise
occurred at the peak region of both the input and the output signals at
the test temperature of -175 °C. This noise, which was more evident at
high frequency as shown in Figure 7, appeared prior to as well after the
cycling. Comparison of the other waveforms of the amplifier that were
obtained at other frequencies and test temperatures before and after the
10 cycle exposure, revealed no distinction. Thus, the thermal cycling
activity performed on the circuit had no influence on its operational
characteristics.

![](media/image5.png){width="2.9972222222222222in"
height="1.9402777777777778in"}

Pre 25 °C

![](media/image6.png){width="2.9993055555555554in" height="1.94375in"}

Pre -175 °C

![](media/image7.png){width="2.997916666666667in"
height="1.9458333333333333in"}

Pre +140 °C

![](media/image8.png){width="2.995833333333333in"
height="1.9340277777777777in"}

Post 25 °C

![](media/image9.png){width="2.995833333333333in"
height="1.9340277777777777in"}

Post -175 °C

![](media/image10.png){width="2.995833333333333in"
height="1.9604166666666667in"}

Post +140 °C

![](media/image11.png){width="2.998611111111111in"
height="1.9513888888888888in"}

Pre 25 °C

![](media/image12.png){width="2.995833333333333in"
height="1.9340277777777777in"}

Pre -175 °C

![](media/image13.png){width="2.995833333333333in"
height="1.9319444444444445in"}

Pre +140 °C

![](media/image14.png){width="2.995833333333333in"
height="1.9458333333333333in"}

Post 25 °C

![](media/image15.png){width="2.995833333333333in"
height="1.926388888888889in"}

Post -175 °C

![](media/image16.png){width="2.997916666666667in"
height="1.9458333333333333in"}

Post +140

![](media/image17.png){width="2.995833333333333in" height="1.925in"}

Pre 25 °C

![](media/image18.png){width="2.998611111111111in"
height="1.945138888888889in"}

Pre -175 °C

![](media/image19.png){width="2.998611111111111in"
height="1.9513888888888888in"}

Pre +140 °C

![](media/image20.png){width="2.995833333333333in"
height="1.9194444444444445in"}

Post 25 °C

![](media/image21.png){width="2.995833333333333in"
height="1.9402777777777778in"}

Post -175 °C

![](media/image22.png){width="2.995833333333333in"
height="1.9340277777777777in"}

Post +140

**Conclusions**

A new prototype operational amplifier based on silicon germanium and
silicon-on-insulator technologies was evaluated for potential use in
extreme temperature environments. The OPA211 device is a low power, high
speed precision operational amplifier with rail-to-rail output swing
capability, and is rated for operation between -40 °C and +125 °C. An
inverter circuit was constructed utilizing the OPA211 chip and a few
passive components. The circuit was evaluated in the temperature range
between -195 °C to +140 °C in terms of signal gain and phase shift, and
supply current. Cold-restart capability, i.e. power switched on while
the device was at cryogenic temperatures, was also investigated. In
addition, the effects of thermal cycling under a wide temperature range
on the operation of this high performance amplifier were determined. The
results from this work indicate that this silicon germanium,
silicon-on-insulator amplifier chip maintained good operation between
+140 °C and -175 °C. The limited thermal cycling had no effect on the
performance of the amplifier and it was able to cold re-start at both
-175 °C and -195 °C. In addition, no physical degradation or packaging
damage was introduced due to either extreme temperature exposure or
thermal cycling. The good performance exhibited by this silicon
germanium, silicon-on-insulator amplifier under short term exposure to
temperatures outside its specified regime renders it as a potential
candidate for use in space exploration missions under extreme
temperatures. Additional and more comprehensive characterization is,
however, required to establish the reliability and suitability of such
devices for long term use in extreme temperature applications.

**References**

1\. Texas Instruments, Inc., "1.1nV/$\sqrt{\text{Hz}}$ Noise, Low Power,
Precision Operational Amplifier in Tiny DFN-8 Package," Data Sheet,
SBOS377 - October 2006.

**Acknowledgments**

This work was performed under the NASA Glenn Research Center, GESS-2
Contract \# NNC06BA07B. Funding was provided from the NASA Electronic
Parts and Packaging (NEPP) Program Task "Reliability of SiGe, SOI, and
Advanced Mixed Signal Devices for Cryogenic Power Electronics".