JPS58223906A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To improve highly the gain without the limit of band, by connecting an input terminal of an inversion amplifier to a collector of a ground-emitter transistor (TR) and coupling input and output terminals of the inversion amplifier with a feedback resistor for forming the collector as an imaginary zero point. CONSTITUTION:An input terminal 12 of the inversion amplifier 11 is connected to the collector 13 of the ground-emitter TR10, and the feedback resistor 15 is couplled between the input and output terminals 14 and 12 of the inversion amplifier 11 to apply negative feedback to the input of the inversion amplifier 11. Further, the base of the TR11 is taken as a signal input terminal 8 of the amplifier circuit and the output terminal 11 of the inversion amplifier 11 is taken as an output terminal 9 of the amplifier circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier circuit of the vine grounding type among amplifier circuits, and an object of the present invention is to provide an amplifier circuit in which the band is not limited even when the gain is set high.

Conventionally, many methods have been proposed to widen the bandwidth of linear ICs.In order to widen the bandwidth of common emitter amplifiers, where the emitter terminal of a bipolar transistor is directly grounded without applying current feedback, the collector It is known that there are cascade amplifier circuits in which base-grounded amplifiers are cascaded on one side. By the way, the cutoff frequency fC of the cascade amplifier circuit is dominated by whichever is lower, where fαl is the cutoff frequency of the common emitter amplifier and fa2 is the collector side cutoff frequency of the common base amplifier, and is usually ,fa1
' There is a relationship of f-a2. - Collector side cutoff frequency chi in 10,000 integrated circuits. 2 is determined by the following: In other words, if the collector side load resistance is L1, the collector height slope is (!ob, the collector substrate slope is (3S), and the next stage input capacitance is the mountain, then f, 12 = 1
/2yrRt, @ (Cob + Os + Oi
) can be expressed as C8 is relatively larger than when constructed from individual parts, and can be expressed as f = 1/2π approximately L-0!1. - 10,000, RL is thick when increasing the gain (necessary, wide, result: Fal) fa2
It may become. That is, even in a cascade type amplifier circuit, if a high gain is to be obtained, the bandwidth is limited and the emitter connection frequency f. It has the disadvantage that it can only obtain a band lower than l. These matters will be explained in more detail with reference to FIG. Figure 1 shows a conventional cascade amplifier circuit, where (1) +2) are input and output terminals, and (3)
is a common emitter transistor, (4) is a common base transistor, and (5) is a load resistor RL. 6) is connected to the emitter terminal (7) of the common base transistor (4), so the -i
, o, the band is wide and the cutoff frequency fa1 is sufficiently low. By the way, common base transistor (4)
The cutoff frequency f (12 is determined by the load resistance Rr and the capacitance CL around it, and in the case of the inside of an integrated circuit, OL
is large because it includes the capacitance between the collector terminal and the substrate, and if the load resistance RL is selected to be large in order to obtain a large gain, the time constant becomes large, and f(12
is less than fal, so the cutoff frequency of the entire amplifier circuit. is determined by 1- (by Frequency f. is #c = 1
/2π0LRL, which is the cutoff frequency of the common emitter transistor (3). This is an amplifier circuit with a narrower band than that of 1.

The present invention connects the input terminal of an inverting amplifier to the collector terminal of the common emitter transistor, connects the input and output terminals of the inverting amplifier using a feedback resistor, and sends a signal to the pin of the common emitter transistor. Since the collector terminal of the common emitter transistor is a virtual zero point, even if the gain is a < ty, the signal is not limited in band like a conventional cascade amplifier. Effects can be obtained.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 6.

FIG. 2 shows the basic circuit of a common emitter amplifier according to the invention. tl'l) (9) is the input terminal and output terminal, OI
is a common emitter transistor, 01) is an input terminal (2)
is the collector terminal α of the common emitter transistor OO
The output terminal 0 of this inverting amplifier Oυ is connected to the output terminal (9).

CO is a feedback resistor Rf- interposed between the input and output terminals (6)-a♦ of the inverting amplifier 0υ, and negative feedback is applied to the input side of the inverting amplifier aυ by this feedback resistor Rf-QQ.

With this configuration, the amplifier circuit shown in FIG. 2 as a whole constitutes a non-inverting amplifier. In addition, the input terminal 0'4 of the inverting amplifier 0, which is connected to the collector r4 and the u''4 of the common emitter transistor OQ, is connected to the feedback resistor R mentioned above.
Since the phase becomes a temporary zero point due to negative feedback due to the 1o field, it is not affected by the valley JiCeQ* around the collector terminal (to), and the voltage gain is zero, so the cutoff frequency pa
l is h in the case of a cascade amplifier circuit. It becomes even higher than 1.

Figure 8 is an equivalent circuit of Figure 2, where A is the gain of the inverting amplifier 01 and Qη is the transconductance gI! 1, the common emitter transistor a1 is expressed as a voltage source. The overall gain Gv of this amplifier circuit is Gv = gml due to the negative feedback in the feedback resistor Rfue.

-1 becomes. Also, when A is displayed including the frequency characteristics, When Gy is passed down to history 1+A Gv=gmItchi・□ A+1 becomes. However, (A+1)τNF=τ.

In this way, the exit frequency f of the inverting amplifier 01) in FIG.
8G is (t+A) times that of no feedback, and the inverting amplifier O
If a common emitter amplifier is used for υ, fsc can be extended to the transition frequency.

Therefore, the cutoff frequency of the common emitter amplifier in the previous stage is 91.
It is easy to exceed.

Figure @4 shows a specific example of an inverting amplifier (II), where (G) is an emitter-grounded transistor with a load resistance of On, and (Z) is an emitter-follower transistor whose base terminal is connected to the collector terminal of the emitter-grounded transistor (to). be. Also, Figure 6 is a schematic diagram of the same combination of Figure 2 and Figure 4. In addition, in Fig. 6, the emitter resistance Qp of the emitter follower transistor (E) acts as the feedback resistance RQ in Fig. 2, and the emitter resistance Qp and the feedback resistance S (A)
This is advantageous when configuring a direct-coupled circuit in integrated circuits, etc.

FIG. 6 shows another embodiment. In this case, the emitter-grounded transistor t11 in Fig. 5 is replaced with a differential amplifier whose emitter is common to both, and the present invention is applied to the collector side of the two transistors (@) that constitute the differential amplifier. has been done. That is, transistor H
@ and CI4@ constitute an inverting amplifier on the collector side of transistors) and (to), respectively, thereby constructing an amplifier circuit similar to that shown in Fig. 2. Note that c14(2) is an input terminal, and -00 is an output terminal.

As described above, according to the present invention, it is possible to achieve a wider band in a common emitter amplifier than when configuring a conventional cascade amplifier. In particular, in cascade amplifiers, when the load resistance on the collector side is increased to increase the gain, or when transistors in integrated circuits have a large collector substrate Φ space, the bandwidth may be limited. However, by applying the present invention, it is possible to obtain a wideband amplifier circuit with high gain.

[Brief explanation of drawings]

Fig. 1 is a connection diagram of a conventional cascade amplifier, Fig. 2 is a basic configuration diagram of the present invention, Fig. 8 is an equivalent circuit of Fig. 2, and Fig. 4 is a main part configuration diagram of Fig. 2. FIG. 6 is a block diagram of an embodiment of an amplifier circuit using the circuit shown in FIG. 4, and FIG. 6 is a block diagram of another embodiment of the amplifier circuit shown in FIG. (8)...Input terminal, (9)...Output terminal, a1)...Emitter (key transistor, 01)...Inverting amplifier, ato...Feedback resistor, @) ...Emitter follower transistor, ◇...Emitter resistance agent Yoshihiro MorimotoFigure 1Figure 3Figure SFigure 6

Claims (1)

[Claims] 1. An input terminal of an inverting amplifier is connected to the collector terminal of the common emitter transistor, the input and output terminals of the inverting amplifier are coupled using a feedback resistor, and a signal is connected to the base terminal of the common emitter transistor. an amplifier circuit that inputs a signal and extracts a signal from an output terminal of the inverting amplifier. 2. The inverting amplifier consists of an emitter-grounded transistor whose base terminal receives a signal, and an emitter-follower transistor whose base terminal is connected to the collector terminal of the emitter-grounded transistor, and which receives a signal from the emitter terminal of the emitter-follower transistor. 2. The amplifier circuit according to claim 1, wherein the amplifier circuit is configured to take out the . 8. The amplifier circuit according to claim 1 and width 2, wherein an emitter resistor of an emitter follower transistor constituting an inverting amplifier is used as the feedback resistor.