Achieve a New Type Frequency Divider Circuit and Application By MOS-HBT-NDR Y.K. LI, K.J. Gan, C. S. Tsai, P.H. Chang and Y. H. Chen Department of Electronic Engineering, Kun-Shan University, Yung-Kang City, Tainan County 710, Taiwan, R.O.C. Abstract The conventional negative-differential-resistance(NDR) is fabricated by Ⅲ - Ⅴ compound material, such as GaAs and InP. It has the advantage of high electron mobility. However it is not very easy to integrate with other devices and circuits. In this paper, we proposed a new NDR device which is composed of metal-oxide-semiconductor- field-effect-transistor (MOS) devices. Because this NDR device is consisted of MOS and BJT devices, we call his novel NDR devices as MOS-BJT-NDR device. Because the current-voltage (I-V) characteristic is N type. This NDR device is so called N-type HBT-NDR device. HBT-NDR devices and their applications are fabricated by the CMOS or Bi-CMOS technique that provided by the national chip implementation center. We design the frequency divider using HBT-NDR devices. This kind of the devices consists of a inductance, a capacitance and NDR device. This frequency divider has a very simple scheme. The different multi-fold of frequency can be controlled by adjusting input frequency and voltage. 。 Key word: negative-differential-resistance(NDR) 、 frequency divider 。 In addition to the use of frequency modulation frequency divider In Fig.2, we use inductors, capacitors as well as a NDR to build up requency divider. L is 1uH, C is 1pH, center frequency of 159MHZ. It is a sine wave input. When V gg = 1.75V, the frequency divider is divided by two. As shown in Figure 3-1. The center frequency is 159MHZ. In Figure 3-2, the frequency divider is divided by three and center frequency is 320MHZ. Fig3-1 and Fig3-2 show frequency divider is divided by two and three under different input frequency respectively. If we change signal amplitude or input DC offset value, it will also has the same property in divider phenomena. N type-MOS-HBT-NDR CIRCUIT Figure 1 is the N type-MOS-HBT-NDR circuit which is composed of three NMOS transistor and a HBT transistor, it is next to the equivalent circuit. Figure 1 is the I-V characteristic curve of Fig.1. Mn1 gate and drain are connected together, it acts like a similar diode (non-linear resistance). Mn2’s gate is controlled by input voltage, it operated like a switch. Mn2 is the key role of NDR circuit. HBT base is connected to mn2 drain and mn1 source, it dominates current in NDR operation. There are three regions in Fig.1. In Region 1, we call it as PDR1 (Positive Differential Region). In this region, mn1 is in saturation region and mn2 is in off state, so HBT operated in active area. The current will increase as input voltage increase. While input voltage is larger enough to turn mn2, mn2 will turn on. When mn2 turn from linear region into saturation, HBT will turn into off state. The current will decrease as input voltage increase in region 2, we call this region as NDR (Negative Differential Region) in Fig.1. In PDR2 region, mn3 transistor operates from linear region into saturation region. The current will increase as input voltage increase because mn3 is in saturation state. Fig. 1 The circuit configuration of N type- MOS-HBT-NDR device. Fig.2 The frequency divider circuit structure. Fig.3-1 Frequency divider output (divide by two). Fig.3-2 Frequency divider output (divide by three). Conclusions We can take use of nonlinear characteristics of NDR devices to implement divider circuit. We made the structure of the circuit to the demand for small. With only a MOS-HBT-NDR, a capacitor and the inductor to confirms the divider circuit. NDR Components can significantly reduce the number of divider circuit. The divider can be different use based on the input frequency, input signal amplitude, input DC offset voltage and input waveform. It is very convenient that the frequency divider can be widely used in various input situation.