Single transistor high linearity and wide dynamic range active inductor

Abstract

In this paper, an active inductor (AI) with high linearity and high dynamic range, including a minimum number of components, is presented. The AI is composed by a single transistor, and by a passive compensation network; the latter allows the control of the values of both the inductance and the series resistance.In order to show the feasibility of the proposed AI for filter applications, a prototype board on a TLX8 substrate with a first-order active band-pass filter has been fabricated and tested. The filter has a center frequency of 2470 MHz (useful for Bluetooth applications) and a measured noise figure (NF) of 9 dB with a À5 dBm P 1 dB compression point, and a 75 dB dynamic range.By considering the filter NF, bandwidth and the P 1 dB, compression point, the dynamic range of the filter from noise floor (À174 dBm/Hz) to P 1 dB compression point is approx. 75 dB. The power consumption is approx. 5 mW. Linear and nonlinear analysis and measurements have shown an unconditionally stable filter response. A table resuming the aforementioned performance is given (see Table I) showing also comparisons with the state of the art. For all these reasons, the natural application of the proposed filter is as a post-selector in radio communications systems, after the low noise amplifier, or as a channel selector in the receiver IF chain. Moreover, it can be used for RF or microwave band selection application, as wakeup radio systems [29], where high dynamic range and selectivity are required without stringent noise performance. CONCLUSIONSWe have proposed a high-Q, high-linearity, and high dynamic range AI, requiring a minimum number of components. A high quality factor band-pass filter including the AI has been designed as a demonstrator. A prototype board on a TLX8 substrate has been fabricated and tested in order to show the AI feasibility for RF and microwave applications. The filter has a center frequency of 2470 MHz, in the Bluetooth frequency range, a measured NF of 9 dB, and a À5 dBm P 1 dB compression point. The resulting 75 dB dynamic range confirms the theoretical predictions and simulation results. The proposed AI, if properly designed, is unconditionally stable in the whole frequency range and can be used in practical applications. We remark that this aspect is usually underestimated in the literature, and, to our best knowledge, only few works give information about AI stability, power handling, and noise. SINGLE TRANSISTOR ACTIVE INDUCTOR 285

Microwave Active Filter Design

“…Now it can be seen that the input impedance of the network is not always inductive [38]. By analyzing the imaginary part, we notice that the imaginary part of the AI impedance has a zero in ω = 0, and it is always positive only if:…”

“…In order to simplify the design, a single active block AI and a compensation network can be also adopted as shown in Figure 5. In Figure 6, an equivalent circuit of the single active block AI [38] is shown. In this case, a simplified model of the capacitance gyrator with a single active block is shown.…”

“…The topology of the compensating network can be designed by means of an optimizer numerical software and the exact values of the network elements can be found by optimization, in order to take into account microstrip discontinuities and lines [38]. The ideal AI application is, of course, in monolithic integrated circuits, but as an example, a preliminary discrete design can be made on microstrip with discrete components.…”

Active inductor-based tunable impedance matching network for RF power amplifier application

“…Table 1 shows the maximum quality factor, power consumption, inductance value, inductance range, and supply voltage of the CASFAI in comparison with some other works. Although the inductance value of the CASFAI is lower than that in [4,7,14], its maximum quality factor as well as its inductance range is higher, while dissipates less power than [4,7,8].…”

“…Usually, simple structures are preferred for RF circuits [7][8][9][10][11]. The configuration of basic flipped-active inductor (FAI) introduced in [9] and [10] is very simple and consists of only two transistors.…”