Y. Zong

Degradation of Power Bipolar Operational Amplifiers in a Mixed Neutron and Gamma Environment

Power operational amplifiers were irradiated in a mixed neutron and gamma radiation environment. These experiments showed that the degradation of the power operational amplifiers shares a great deal of characteristics with that of the low signal devices (e.g., shift of the input offset voltage, increase of the input bias currents, and degradation of the frequency behavior). However, other phenomena were observed without equivalence in the family (linear dependence of the inverse of the quiescent current on the neutron fluence, more significant degradation of the negative output current and collapse of the primary operational amplifiers). These phenomena were explained from the special characteristics of the output stage, optimized to provide a current of several amperes. Finally, even though power devices are especially sensitive to radiation damage, some of the tested devices are suitable for radiation levels on the order of 5 ldr 1013 - 1014 n ldr cm-2 in case the whole electronic system, in which the device is integrated, is carefully designed.

Inactivity Windows in Irradiated CMOS Analog Switches

Radiation tests have shown the existence of inactivity windows in analog switches. It means that the devices lose their ability to switch between ON and OFF states if the total radiation dose is placed between two characteristic values. Once the total radiation dose goes beyond the top value of the window, the switching ability reappears. A physical mechanism based on the evolution of the threshold voltage of irradiated NMOS transistors is proposed in this paper. Finally, consequences of inactivity windows in the conception of radiation tests are discussed

New Details About the Frequency Behavior of Irradiated Bipolar Operational Amplifiers

The frequency behavior of a bipolar operational amplifier (op amp) is always expected to worsen when the device is irradiated. In other words, parameters like the slew rate and the gain-bandwidth product are to decrease after either neutron or gamma tests. However, some neutron and TID tests performed on a large variety of bipolar op amps have shown that the evolution of the frequency behavior is not as simple as it is usually believed. In fact, there is evidence of an increasing influence of the power supply values on the former parameters, which can be extremely important in some devices. Also, the relationship among different frequency parameters has been investigated and, finally, an interesting and scarcely reported phenomenon is depicted. This phenomenon is the appearance of spontaneous oscillations in fed-back op amps, without doubt related to the modification of the gain and phase margins of the devices

Radiation effects on XFET voltage references

XFET references make up a new kind of voltage references different from the popular band-gap or buried Zener devices. These references are built by means of a reference cell consisting of a couple of p-channel junction field effect transistors with different pinch-off voltage values and an operational amplifier for the purpose of improving the output characteristics of the whole device. An irradiation in a mixed gamma and neutron environment was performed at the Portuguese Research Reactor for a complete characterization of the devices. Some of the parameters were measured during the irradiation while the rest of them were obtained once the samples were removed from the neutron facility. Experimental results show that some references belonging to this class are interesting candidates for a design of radiation-tolerant electronic systems based on COTS devices.

Evolution of lowest supply voltage and hysteresis phenomena in irradiated analog CMOS switches

Radiation tests on CMOS analog switches were carried out in order to select the most tolerant device for future use in the cryogenic system of the CERN large hadron collider. After irradiation, the devices showed some interesting changes related to the power supplies: an increase in the lowest supply voltage capable of biasing correctly the devices; some devices cannot work with TTL logic levels. In addition, hysteresis phenomena appear.

Neutron effects on short circuit currents of op amps and consequences

Discrete bipolar operational amplifiers were irradiated with neutrons in order to study the evolution of the short circuit currents. Also, this paper explores the effect of the reduction of this current in devices based on operational amplifiers.

Rad-Tol Pt-100 Isolation Amplifiers for the LHC Cryogenic System

The cryogenic system of the LHC will use Pt-100 sensors to measure temperatures between 40-300K and isolation devices will be used. The selected commercial components must be rad-tolerant since a total radiation dose of 5E12 n/cm2 &100 Gy is expected during ten years of the LHC lifetime. Neutron tests in this family of devices were performed and the results are shown in this paper.

Degradation of capacitor-based isolation amplifiers under neutron and gamma radiation

Some samples of the ISO122 and the ISO124, capacitor-based isolation amplifiers from Texas Instruments, were irradiated in a neutron & gamma environment in order to investigate their tolerance to the total radiation dose. After the experimental data, the most sensitive parameters were the offset voltages, transmission gain and the typical output error. In any case, devices are still operative after receiving 2.2middot1013 1-MeV nmiddotcm-2 & 235 Gy(Si).

Radiation-tolerant supervisory circuits

This paper is devoted to the description of the evolution of different commercial microprocessor supervisory circuits under neutron radiation. After the irradiation, the tested devices showed some interesting changes: the increase of supply current and the duty cycles for watchdog timer. It was also observed that in some devices existed threshold voltage hysteresis and their trigger level was not in the usual TTL range of 0-5V.

Supervisory circuits in a mixed neutron and gamma radiation environment

This paper describes the evolution of different commercial microprocessor supervisory circuits under neutron and gamma radiation. After the irradiation, the tested devices showed some interesting changes: an increase of supply current and the period of watchdog timer. It was also observed that threshold voltage hysteresis and the shift of TTL trigger level appeared in some devices.