JPH0513047Y2 - - Google Patents
Info
- Publication number
- JPH0513047Y2 JPH0513047Y2 JP1986177741U JP17774186U JPH0513047Y2 JP H0513047 Y2 JPH0513047 Y2 JP H0513047Y2 JP 1986177741 U JP1986177741 U JP 1986177741U JP 17774186 U JP17774186 U JP 17774186U JP H0513047 Y2 JPH0513047 Y2 JP H0513047Y2
- Authority
- JP
- Japan
- Prior art keywords
- amplifier circuit
- capacitor
- negative feedback
- transistor
- terminal voltage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000003990 capacitor Substances 0.000 claims description 39
- 101000684181 Homo sapiens Selenoprotein P Proteins 0.000 claims 3
- 102100023843 Selenoprotein P Human genes 0.000 claims 3
- 229940119265 sepp Drugs 0.000 claims 3
- 238000010586 diagram Methods 0.000 description 3
- 230000001052 transient effect Effects 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 230000035939 shock Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
Description
【考案の詳細な説明】
(イ) 産業上の利用分野
本考案は、前段に差動増幅回路を、後段に
SEPP（シングルエンデツドプツシユプル）増幅
回路を備える電力増幅回路に関するもので、特に
電源を繰り返しオンオフさせた場合においても、
電源オンから増幅回路が動作を開始する迄の時間
を一定とすることが出来る電力増幅回路に関す
る。
(ロ) 従来の技術
前段に差動増幅回路を、後段にSEPP増幅回路
を備え、前記SEPP増幅回路の出力端から前記差
動増幅回路に負帰還を施こして成る電力増幅回路
は、例えば実開昭57−69316号公報に記載されて
いる。前記電力増幅回路は、第２図に示される如
く、入力端子１に印加される入力信号を、まず差
動接続された第１及び第２トランジスタ２及び３
を含む差動増幅回路４で増幅し、その後、前置駆
動トランジスタ５、第１及び第２駆動トランジス
タ６及び７、第１及び第２出力トランジスタ８及
び９を含むSEPP増幅回路１０で増幅するもので
ある。
しかして、出力端子１１に得られる増幅された
出力信号は、第１及び第２帰還抵抗１２及び１３
と帰還コンデンサ１４から成る帰還回路１５を介
して第２トランジスタ３のベースに帰還されてお
り、第２図の回路は全体として負帰還型の電力増
幅回路を構成している。
(ハ) 考案が解決しようとする問題点
第２図の電力増幅回路の場合、第１及び第２帰
還抵抗１２及び１３が大である為、帰還コンデン
サ１４の放電時定数が大になる。その為、電源ス
イツチのオンオフを繰り返すと、前記帰還コンデ
ンサ１４の残り電荷に起因して、動作開始時間が
早くなり、前段増幅回路の過渡状態が電力増幅回
路で増幅され、シヨツク音を発生する等の問題が
あつた。
(ニ) 問題点を解決するための手段
本考案は、上述の点に鑑み成されたもので、ベ
ースにコンデンサが接続されたトランジスタを含
み、電源に重畳されるリツプルを除去するリツプ
ルフイルタと、前記コンデンサの端子電圧に応じ
てSEPP増幅回路に動作電流を供給する電流源ト
ランジスタと、前記SEPP増幅回路の出力端から
前記差動増幅回路に負帰還を施こす為の負帰還コ
ンデンサと、前記リツプルフイルタ回路のコンデ
ンサの端子電圧と前記負帰還コンデンサの端子電
圧とを比較し、前記負帰還コンデンサの放電を行
なう放電トランジスタとを有する点を特徴とす
る。
(ホ) 作用
本考案に依れば、電源をオフするとリツプルフ
イルタを構成するコンデンサの端子電圧が低下
し、それに応じて放電トランジスタがオンするの
で、電源オフ後速やかに負帰還コンデンサの放電
を行なうことが出来る。その為、次に電源をオン
するときには、前記負帰還コンデンサが確実に放
電されており、電源オンから動作開始迄の時間を
常に一定にすることが出来る。
(ヘ) 実施例
第１図は、本考案の一実施例を示す回路図で、
１６は前段差動増幅回路、１７は後段SEPP増幅
回路、１８は第１及び第２負帰還抵抗１９及び２
０と負帰還コンデンサ２１とから成り、出力端子
２２に得られる出力信号を差動増幅回路１６の第
２トランジスタ２３のベースに帰還する負帰還回
路、２４は電源（＋Vcc）とアースとの間に直列
接続された抵抗２５及びコンデンサ２６とベース
に前記コンデンサ２６の一端が接続されたトラン
ジスタ２７とから成り、電源に重畳されるリツプ
ルを除去する為のリツプルフイルタ、２８は前記
コンデンサ２６の端子電圧に応じて、SEPP増幅
回路１７に動作電流を供給する電流源トランジス
タ、２９及び３０は前記トランジスタ２７のエミ
ツタとアースとの間に直列接続されるダイオード
及び抵抗、３１はベースが前記ダイオード２９と
抵抗３０との接続中点に接続され、エミツタが前
記負帰還コンデンサ２１の一端に接続された放電
トランジスタである。
電源をオンすると、リツプルフイルタ２４のコ
ンデンサ２６の充電が開始され、トランジスタ２
７のベース電圧が上昇を開始する。そして、前記
コンデンサ２６の端子電圧が所定値に達すると、
前記トランジスタ２７がオンし、差動増幅回路１
６への動作電流が供給されるとともに、電流源ト
ランジスタ２８がオンし、SEPP増幅回路１７へ
の動作電流が供給される。電源オン直後において
は、入力端子３２が所定値にバイアスされ、差動
増幅回路１６を構成する第１トランジスタ３３の
ベース電圧は所定値になるが、負帰還コンデンサ
２１が存在する為に第２トランジスタ２３のベー
ス電圧は低いままである。その為、第１トランジ
スタ３３がオフ、第２トランジスタ２３がオンと
なり、入力端子３２に印加される入力信号は
SEPP増幅回路に伝達されない。時間の経過に従
つて、負帰還コンデンサ２１の充電が進み、その
端子電圧が上昇し、差動増幅回路１６の第１及び
第２トランジスタ３３及び２３のベース電圧が略
等しくなると、入力端子３２に印加された入力信
号が、差動増幅回路１６で増幅され、第１トラン
ジスタ３３のコレクタからSEPP増幅回路１７に
伝送される。従つて、電力増幅回路の増幅動作
は、電源オンから一定時間（TS）経過した後に
開始される。
電源オンから動作開始迄の過渡状態、及び定常
状態においては、リツプルフイルタ２４のコンデ
ンサ２６の端子電圧が十分に高く、放電トランジ
スタ３１のベース電圧はエミツタ電圧よりも十分
に高くなる。その為、前記放電トランジスタ３１
は逆バイアス状態となり、回路動作に何ら寄与し
ない。尚、定常時における増幅動作は、従来の電
力増幅回路と同一に付、説明を省略する。
電源をオフにすると、電源電圧は電源自体の時
定数に従つて急激に低下する。そして、リツプル
フイルタ２４のコンデンサ２６の端子電圧もそれ
に応じて低下する。前記コンデンサ２６の放電が
進み、放電トランジスタ３１のベース電圧が所定
値に低下すると、前記放電トランジスタ３１が順
バイアス状態になりオンする。その為、負帰還コ
ンデンサ２１は、前記放電トランジスタ３１のコ
レクタ・エミツタ路により急速放電される。リツ
プルフイルタ２４のコンデンサ２６の端子電圧の
低下速度は比較的速く、放電トランジスタ３１の
ベース電圧も速く低下するので、負帰還コンデン
サ２１は電源オフ後直ちに完全放電状態となる。
上述の如く、電源をオフしたのち、負帰還コン
デンサ２１が速やかに放電される為、電源のオン
オフを繰り返しても、増幅動作が開始する迄の時
間（TS）は変化しない。従つて、電力増幅回路
の動作開始が異常に早まり、前段の過渡状態が増
幅されシヨツク音を発生する等の問題が生じな
い。
(ト) 考案の効果
以上述べた如く、本考案に依れば、電源オンオ
フを繰り返しても、増幅動作の開始時間が変化し
ない電力増幅回路を提供出来る。その場合、リツ
プルフイルタを構成するコンデンサの端子電圧と
負帰還コンデンサの端子電圧とを比較することに
より、放電トランジスタを動作させているので、
電源オフ時に正確に動作し、定常時の増幅動作に
悪影響を及ぼさない急速放電動作を行なわせるこ
とが出来る。そして、前記急速放電動作は、従来
の電力増幅回路に、ダイオード、抵抗、及びトラ
ンジスタを付加するだけで行ない得るので、IC
（集積回路）化に適した電力増幅回路を提供出来
る。 [Detailed description of the invention] (A) Industrial application field This invention uses a differential amplifier circuit in the front stage and a
This is a power amplifier circuit equipped with a SEPP (single-ended push-pull) amplifier circuit, which is particularly effective when the power supply is repeatedly turned on and off.
This invention relates to a power amplifier circuit that can keep constant the time from when the power is turned on until the amplifier circuit starts operating. (B) Prior Art A power amplifier circuit that has a differential amplifier circuit in the front stage and a SEPP amplifier circuit in the rear stage, and is configured by applying negative feedback from the output terminal of the SEPP amplifier circuit to the differential amplifier circuit, is described, for example, in Japanese Utility Model Application Publication No. 57-69316. As shown in Fig. 2, the power amplifier circuit first converts an input signal applied to an input terminal 1 into a differentially connected first and second transistors 2 and 3.
The output signal is amplified by a differential amplifier circuit 4 including a pre-driver transistor 5, first and second drive transistors 6 and 7, and first and second output transistors 8 and 9. The amplified output signal obtained at the output terminal 11 is fed back through first and second feedback resistors 12 and 13.
and a feedback capacitor 14 , and the circuit in Fig. 2 as a whole constitutes a negative feedback type power amplifier circuit. (c) Problems to be solved by the invention In the case of the power amplifier circuit in Fig. 2, the first and second feedback resistors 12 and 13 are large, so the discharge time constant of the feedback capacitor 14 becomes large. As a result, when the power switch is repeatedly turned on and off, the remaining charge in the feedback capacitor 14 causes the operation start time to become earlier, and the transient state of the previous stage amplifier circuit is amplified by the power amplifier circuit, causing a shock sound and other problems. (D) Means for solving the problems The present invention has been made in consideration of the above-mentioned points, and is characterized by comprising a ripple filter including a transistor with a capacitor connected to its base, which removes ripples superimposed on the power supply, a current source transistor which supplies an operating current to a SEPP amplifier circuit according to the terminal voltage of the capacitor, a negative feedback capacitor for providing negative feedback from the output terminal of the SEPP amplifier circuit to the differential amplifier circuit, and a discharge transistor which compares the terminal voltage of the capacitor of the ripple filter circuit with the terminal voltage of the negative feedback capacitor and discharges the negative feedback capacitor. (E) Function According to the present invention, when the power supply is turned off, the terminal voltage of the capacitor constituting the ripple filter drops, and the discharge transistor turns on accordingly, so that the negative feedback capacitor can be discharged quickly after the power supply is turned off. Therefore, when the power supply is turned on again, the negative feedback capacitor is reliably discharged, and the time from power on to the start of operation can be always constant. (F) Example Fig. 1 is a circuit diagram showing an example of the present invention,
16 is a front-stage differential amplifier circuit, 17 is a rear-stage SEPP amplifier circuit, 18 is a first and second negative feedback resistors 19 and 20.
The negative feedback circuit 24 is made up of a resistor 25 and a negative feedback capacitor 21, and feeds back an output signal obtained at an output terminal 22 to the base of a second transistor 23 of the differential amplifier circuit 16. The ripple filter 24 is made up of a resistor 25 and a capacitor 26 connected in series between a power supply (+Vcc) and the ground, and a transistor 27 with one end of the capacitor 26 connected to its base, and is used to remove ripples superimposed on the power supply. The current source transistor 28 supplies an operating current to the SEPP amplifier circuit 17 in response to the terminal voltage of the capacitor 26. The diodes 29 and 30 are connected in series between the emitter of the transistor 27 and the ground, and a resistor. The discharge transistor 31 has its base connected to the midpoint of the connection between the diode 29 and the resistor 30, and its emitter connected to one end of the negative feedback capacitor 21. When the power supply is turned on, charging of the capacitor 26 of the ripple filter 24 starts, and the transistor 27 is turned on.
Then, when the terminal voltage of the capacitor 26 reaches a predetermined value,
The transistor 27 is turned on, and the differential amplifier circuit 1
6, the current source transistor 28 turns on, and an operating current is supplied to the SEPP amplifier circuit 17. Immediately after the power is turned on, the input terminal 32 is biased to a predetermined value, and the base voltage of the first transistor 33 constituting the differential amplifier circuit 16 becomes a predetermined value, but the base voltage of the second transistor 23 remains low due to the presence of the negative feedback capacitor 21. Therefore, the first transistor 33 turns off and the second transistor 23 turns on, and the input signal applied to the input terminal 32 becomes
The input signal is not transmitted to the SEPP amplifier circuit. As time passes, the charging of the negative feedback capacitor 21 progresses, the terminal voltage rises, and when the base voltages of the first and second transistors 33 and 23 of the differential amplifier circuit 16 become substantially equal, the input signal applied to the input terminal 32 is amplified by the differential amplifier circuit 16 and transmitted from the collector of the first transistor 33 to the SEPP amplifier circuit 17. Therefore, the amplifying operation of the power amplifier circuit starts after a certain time (T S ) has elapsed since the power is turned on. In the transient state from when the power is turned on to when operation starts, and in the steady state, the terminal voltage of the capacitor 26 of the ripple filter 24 is sufficiently high, and the base voltage of the discharge transistor 31 becomes sufficiently higher than the emitter voltage. Therefore, the discharge transistor 31
is in a reverse bias state and does not contribute to the circuit operation. Incidentally, the amplifying operation in the steady state is the same as that of the conventional power amplifier circuit, so the explanation will be omitted. When the power supply is turned off, the power supply voltage drops rapidly according to the time constant of the power supply itself. The terminal voltage of the capacitor 26 of the ripple filter 24 also drops accordingly. When the discharge of the capacitor 26 progresses and the base voltage of the discharge transistor 31 drops to a predetermined value, the discharge transistor 31 becomes in a forward bias state and turns on. Therefore, the negative feedback capacitor 21 is rapidly discharged by the collector-emitter path of the discharge transistor 31. The rate at which the terminal voltage of the capacitor 26 of the ripple filter 24 drops is relatively fast, and the base voltage of the discharge transistor 31 also drops quickly, so that the negative feedback capacitor 21 is completely discharged immediately after the power supply is turned off. As described above, since the negative feedback capacitor 21 is quickly discharged after the power supply is turned off, the time (T S ) until the amplifying operation starts does not change even if the power supply is turned on and off repeatedly. Therefore, problems such as abnormally early start of operation of the power amplifier circuit, amplified transient states in the previous stage, and the generation of shock noise do not occur. (G) Effects of the Invention As described above, this invention can provide a power amplifier circuit whose amplification start time does not change even if the power is repeatedly turned on and off. In this case, the discharge transistor is operated by comparing the terminal voltage of the capacitor that constitutes the ripple filter with the terminal voltage of the negative feedback capacitor.
This allows the IC to perform a rapid discharge operation that operates accurately when the power supply is off and does not adversely affect the amplification operation during normal operation. The rapid discharge operation can be performed simply by adding a diode, resistor, and transistor to a conventional power amplifier circuit.
It is possible to provide a power amplifier circuit suitable for (integrated circuit) implementation.
第１図は、本考案の一実施例を示す回路図、及
び第２図は従来の電力増幅回路を示す回路図であ
る。
１６……差動増幅回路、１７……SEPP増幅回
路、１８……負帰還回路、２１……負帰還コンデ
ンサ、２４……リツプルフイルタ、２６……コン
デンサ、３１……放電トランジスタ。
FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional power amplifier circuit. 16 ...Differential amplifier circuit, 17 ...SEPP amplifier circuit, 18 ...Negative feedback circuit, 21...Negative feedback capacitor, 24 ...Ripple filter, 26...Capacitor, 31...Discharge transistor.
Claims (1)
を有する電力増幅回路において、ベースにコンデ
ンサが接続されたトランジスタを含み、電源に重
畳されるリツプルを除去するリツプルフイルタ
と、前記コンデンサの端子電圧に応じて前記
SEPP増幅回路に動作電流を供給する電流源トラ
ンジスタと、前記SEPP増幅回路の出力端から前
記差動増幅回路に負帰還を施こす為の負帰還コン
デンサと、前記リツプルフイルタのコンデンサの
端子電圧と前記負帰還コンデンサの端子電圧とを
比較し、電源オフ時に前記コンデンサの端子電圧
が所定値に低下したときオンして前記負帰還コン
デンサの放電を行なう放電トランジスタとを備え
る点を特徴とする電力増幅回路。 In a power amplifier circuit having a differential amplifier circuit in the front stage and an SEPP amplifier circuit in the rear stage, a ripple filter including a transistor with a capacitor connected to the base and removing ripples superimposed on the power supply, and a terminal voltage of the capacitor According to the above
A current source transistor that supplies an operating current to the SEPP amplifier circuit, a negative feedback capacitor for providing negative feedback from the output terminal of the SEPP amplifier circuit to the differential amplifier circuit, and a terminal voltage of the capacitor of the ripple filter. and a discharge transistor that compares the terminal voltage of the negative feedback capacitor and turns on when the terminal voltage of the capacitor drops to a predetermined value when the power is off to discharge the negative feedback capacitor. circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1986177741U JPH0513047Y2 (en) | 1986-11-19 | 1986-11-19 |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1986177741U JPH0513047Y2 (en) | 1986-11-19 | 1986-11-19 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6383810U JPS6383810U (en) | 1988-06-01 |
| JPH0513047Y2 true JPH0513047Y2 (en) | 1993-04-06 |
Family
ID=31119231
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1986177741U Expired - Lifetime JPH0513047Y2 (en) | 1986-11-19 | 1986-11-19 |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0513047Y2 (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6135420A (en) * | 1984-07-27 | 1986-02-19 | Tanaka Kikinzoku Kogyo Kk | Composite blank material for spectacle frame |
-
1986
- 1986-11-19 JP JP1986177741U patent/JPH0513047Y2/ja not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6135420A (en) * | 1984-07-27 | 1986-02-19 | Tanaka Kikinzoku Kogyo Kk | Composite blank material for spectacle frame |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6383810U (en) | 1988-06-01 |
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